MODERN  STEAM  ENGINES: 

AN  ELEMENTARY  TREATISE  UPON  THE  STEAM  ENGINE,  WRITTEN  IN  PLAIN  LANGUAGE; 
FOR  USE  IN  THE  WORKSHOP  AS  WELL  AS  IN  THE  DRAWING  OFFICE. 

GIVING 

FULL  EXPLANATIONS 

OP 

THE  CONSTRUCTION  OF  MODERN  STEAM  ENGINES; 

INCLUDING 

DIAGRAMS  SHOWING  THEIR  ACTUAL  OPERATION; 

TOGETHER  WITH 

COMPLETE  BIT  SIMPLE  EXPLANATIONS  OF  THE  OPERATIONS  OP  VARIOUS  KINDS  OP  VALVES,  VALVE  MOTIONS,  AND 

LINK  MOTIONS,  ETC.,  THEREBY  ENABLING  THE  ORDINARY  ENGINEER  TO  CLEARLY  UNDERSTAND  THE 

PRINCIPLES  INVOLVED  IN  THEIR  CONSTRUCTION  AND  USE,  AND  TO  PLOT  Our 

THEIR  MOVEMENTS  UPON  THE  DRAWING  BOARD. 

BY  JOSHTJ^  ROSE,   M.  E., 

Author  of  "The  Complete  Practical  Mnehiii!*!,"  "Mechanical  Drawing  Self-Taught,"  "The  Pattern  Maker1!  Astittant* 

"Modern  Machine  Shop  Practice,"  "The  Slide  Valve." 


Illustrated  by  Four  Hundred  and  Fifty-three  Engravings. 

'4   A'AJF  EDITIO.\\    REVISED  AND   IMPROVED. 


OF  THE 

TJNIVERSITT) 

A-  PHILADELPHIA: 

HENRY    CAREY    BAIRD    &   CO., 

INDUSTRIAL  PUBLISHERS.   BOOKSELLERS  AND  IMPORTERS, 

810    WALNUT    STREET. 

LONDON  : 

SAMPSON    LOW,    MARSTON   &   CO.,   LIMITED, 

ST.  DONSTAN'S  HOUSE,  FETTER  LANE,  FLEET  STREET. 
1893. 


COPYRIGHT  BY 

JOSHUA  ROSE, 

1886. 


COPYRIGHT   BY 

JOSHUA  ROSE, 

1893. 


PRINTED  AT 

COLLINS  PRINTING  HOUSfc, 

PHILADELPHIA,  U.  8.  A. 


• 
.UNIVERSIT 

PREFACE  TO  THE   REVISED   EDITION. 


IX  the  revision  of  this  work  all  the  necessary  corrections  have  been  made  to  the  first  edition  and  new 
subject  matter  has  been  added  upon  Triple  Expansion  Engines,  thus  bringing  the  work  up  to  date  and 
greatly  adding  to  its  usefulness.  ~  ,*. 

The  distinguishing  features  of  the  book  are  maintained  in  the  revised  edition ;  the  object  having  been 
to  begin  at  the  elementary  parts  of  steam  engines,  and,  after  treating  them  exhaustively  in  the  language  used 
in  the  workshop,  to  pass  on  and  show  how  these  elementary  parts  and  mechanisms  are  employed  in  practice 
in  various  kinds  of  engines. 

The  various  elasses  of  slide-valve  and  link  motions  have  been  treated  very  fully,  because  in  the  construc- 
tion of  the  valve  motion  chiefly  lie  the  distinguishing  features  of  most  engines. 

The  diagrams  explaining  the  action  of  each  valve  and  link  motion  have  been  obtained  by  moving  the 
engine  throughout  a  revolution,  and  measuring  the  port  openings,  both  for  the  admission  and  exhaust,  at 
each  inch  of  piston  motion.  These  diagrams  therefore  represent  the  actual  workings  of  the  valves  and  link 
motions. 

In  the  examples,  engines  of  as  nearly  as  possible  the  same  size  have  been  shown,  so  as  to  enable  the 
reader  to  compare  the  action  of  the  different  valve  motions,  and  to  make  this  comparison  still  more  com- 
pl.te,  a  diagram  of  the  action  of  each  class  of  valve  motion  is  given,  as  well  as  diagrams  of  the  same  valve 
motion,  under  different  conditions  of  eccentric  position  and  valve  travel. 

The  author  has  endeavored  to  omit  nothing  that  is  essential  to  those  who  may  begin  their  studies  of  the 
steam  engine  from  the  pages  of  this  book,  and  pains  have  been  taken  to  render  it  easy  to  follow  the  text. 
To  this  end  the  following  means  have  been  employed  : 

When  a  certain  mechanism  is  to  be  considered,  the  engravings  first  show  it  as  a  whole  and  explain  its 
general  action.  It  is  then  treated  in  detail  and  moved  through  its  various  positions,  a  separate  engraving 
showing  each  new  condition,  and  a  diagram  showing  the  action  under  each  condition. 

w 


vi  PREFACE  TO   THE  REVISED  EDITION. 

The  engravings  have  been  made  large  and  are,  in  many  cases,  repeated,  so  as  to  render  them  easy  to 
follow  and  thus  avoid  turning  to  back  pages. 

Each  subject  is  complete  in  itself,  hence  some  subjects  are  treated  in  repetition.  This  possesses  no  dis- 
advantage, because  it  saves  turning  to  back  pages  when  studying  particular  mechanisms  or  movements, 
while  it  serves  the  learner  as  a  review.  Thus  the  effect  of  the  connecting-rod  in  varying  the  piston  speed 
is  treated  of  in  connection  with  Common  Slide-%-alve  engines,  Adjustable  Cut-off  engines,  Automatic  Cut-off 
engines,  Shifting  Eccentrics,  Diagrams  for  designing  Valve  Motions  and  Link  Motions. 

Again,  the  subject  of  diagrams  for  designing  valve  motions  and  for  investigating  the  action  of  valve 
motions  is  treated  in  several  different  ways,  each  explaining  the  groundwork  upon  which  such  diagrams  arc 
based.  This  lays  a  solid  foundation  upon  which  the  reader  may  afterwards  proceed  without  difficulty, 
and  it  is  hoped  and  believed  that  the  work  will  be  found  full  and  clear  in  its  treatment,  and  easy  to 
follow. 

JOSHUA  ROSE. 

FoitKST   HlLI.,, 

LONDON,  ENGLAND. 

January  6,  1893. 


CONTENTS. 


CHAPTER  I. 

CLASSIFICATION      <>K      STKAM       KNMNKS— THK      COMMON 
SL1DK    VALVK     KXCilXK. 

PAUE 

The  Various  Kinds  of  Steam  Engines     .        .     11 

The  Common  Slide- Valve  Engine    .        .         .13 

The  General  Action  of  a  Common  Slide- Valve     14 

Cylinder  Ports 15 

Slide- Valve  without  Lap;  The  Steam  and  Ex- 
haust Kelt's  of  the  Valve  and  of  the  Steam 
Lap;  The  Effect  of  Steam  Lap  ...  16 

The  Throw  of  the  Eccentric ;  Angular  Advance 
of  the  Eccentric ;  Valve  Lead  .  .  17 

The  Positions  of  the  Eccentric  when  the  Valve 
has  neither  Lap  nor  Lead,  and  when  it  has 
both  Lap  and  Lead  ;  Exhaust  Lap  and  its 
EiUrt  .  .  18 

Cushioning  and  its  Effect;  Clearance  and  its 
E fleet;  Valve  Travel  ...  .19 

Valve  Over-travel  and  its  Effect ;  Irregularity 
of  the  Piston  Motion 20 

The  Effect  of  the  Connecting- Rod  in  Causing 
the  Piston  Motion  to  be  Irregular ;  The 
Relative  Movements  of  the  Piston  and 
Crank 21 

The  Position  of  Eccentric  necessary,  under  dif- 
ferent Conditions,  to  give  a  certain  amount 
of  Valve  Lead 22 

The  Effect  of  a  Rock-Shaft  upon  the  Action  of 
a  Common  Slide- Valve  .  .  .  .23 

Diagram,  showing  the  Action  of  a  Common 
Slide- Valve  without  Lap  .  .  .  .24 

Diagram  of  the  Action  of  the  Valve  when  Steam 
Lap  is  added 25 

Diagram  of  Valve  Action  when  the  Valve  has 
Over-Travel ;  Diagram  of  a  Standard  Ameri- 
can Passenger  Locomotive  .  .  .26 

The    Expansion   of   Steam,  and  the    Gain   in 
Economy  it  gives 27 


PAGE 

Diagram  of  Steam  Expansion ;  The  Construc- 
tion of  the  Allen  Valve  ...  28 

The  Allen  Valve  in  Position  for  the  Various 
Events,  as  at  Cut-off,  etc. ;  The  Proportions 
of  the  Allen  Valve  .  .  .  .  .29 

Diagrams  Comparing  the  Action  of  the  Allen 
Valve  with  that  of  the  Common  Slide- Valve  30 

The  Allen  Valve  Cutting  Off  at  Half-Stroke    .     31 

Summary  of  the  Action  of  the  Allen,  and  of 
the  Common  Slide- Valves  .  32 


DIAGRAMS       FOR 


CHAPTER  II. 

liKSKlXISG       VALVE 
MECHANISMS. 


MOTIONS       OR 


The  Path  of  Motion  and  the  Throw  of  an 
Eccentric;  To  find  how  much  a  Given 
Eccentric  Throw  moves  the  Valve  .  .  33 

The  Crank-Pin  and  Piston  Movements ;  The 
Effect  of  the  Connecting- Rod  in  Varying  the 
Piston  Movement 34 

The  Circles  Representing  the  Path  of  the  Eccen- 
tric and  of  the  Crank ;  Finding  the  Position 
of  the  Eccentric  from  that  of  the  Crank  .  35 

Finding  the  Position  of  the  Crank  from  that  of 
the  Piston  ;  The  Angularity  of  the  Eccentric- 
Rod  and  its  Effect;  Finding  the  Piston, 
Crank  and  Eccentric  Positions  when  the 
Valve  has  no  Lap 36 

Finding  the  Positions  of  the  Parts  when  the 
Valve  has  Lap  ....  .37 

Constructing  a  Diagram  for  Finding  the  Effects 
of  Given  Valve  Proportions  .  .  .38 

Equalizing  the  Points  of  Cut-off  by  Unequal 
Lap,  or  by  Unequal  Lead  ;  Finding  the  Points 
of  Release  and  of  Compression  .  .  .39 

(vii) 


Till 


CONTEXTS. 


PAGE 

Plotting  Valve  Motions  when  the  Points  of  Cut- 
off are  not  to  be  Equalized  .  .  .40 

Valves  with  Equal  and  Unequal  Lips       .         .     41 

The  Paths  of  the  Eccentric  and  Crank,  for  the 
Forward  Stroke 42 

Valve  Positions  for  Various  Eccentric  Positions 
during  Forward  Stroke  .  .  .  .43 

The  Paths  of  the  Eccentric  and  Crank  on  the 
Backward  Stroke 44 

Valve  Positions  for  Various  Eccentric  Positions 
on  the  Back-Stroke 45 

Finding  the  Point  of  Admission         .         .        .46 

Names  of  the  Lines  of  Zeuner's  Diagram          .     47 

The  Construction  of  Zeuner's  Diagram     .         .     48 

Constructing  a  Zeuner  Diagram        .         .         .49 

Tracing  the  Movements  of  the  Piston  Crank 
and  Eccentric  on  the  Diagram  .  .  .50 

Locating  the  Events  Depending  on  the  Exhaust 
Lap  .  ......  51 

Finding  the  Eccentric  Position  and  the 
Points  of  Cut-off  and  Exhaust  for  a  given 
Valve .52 

The  Influence  of  the  Connecting-Rod  in  Vary- 
ing the  Point  of  Cut-off  .  .  .  .53 

Diagram  of  Valve  Motion,  when  a  Slotted 
Cross-Head  is  used  instead  of  a  Crank  .  54 

Finding  the  Crank  Position  for  Equalized 
Points  of  Cut-off 55 

The  Points  of  Exhaust;  Harmonizing  the 
Points  of  Cut-off  with  the  Piston  Motion  .  56 

Summary  of  the  foregoing  Diagram  Solutions ; 
Finding  the  Amount  of  Steam  Lap,  of 
Valve  Travel  and  the  Eccentric  Position 
necessary  for  a  given  amount  of  Lead  and 
given  Points  of  Cut-off  .  .  .  .57 

Finding  the  necessary  amount  of  Exhaust  Lap     58 

Constructing  a  Diagram  to  Show  the  Opening 
and  Closure  of  the  Steam  and  Exhaust  Ports 
of  a  given  Valve  Motion  .  .  .  .59 

Tracing,  on  the  foregoing  Diagram,  the  Open- 
ing and  Closing  of  the  Ports  during  one  Pis- 
ton-Stroke .  63 


CHAPTER  III. 

LINK    MOTIONS   AND   REVERSING   GEARS. 

General  Description  of  Stephenson's  Link 
Motion 64 

The  Link  in  Full  Forward,  and  in  Full  Back- 
ward Gear  ....  .  .  65 

The  Link  in  Mid-Gear ;  The  Action  of  the 
Parts  .  66 


PAGE 

Drawing  a  Link  Motion  .        .        .        .67 

Finding  the  Positions  of  the  Upper  End  of  the 
Link  in  Full  Forward  Gear;  Finding  the 
Positions  of  the  Link  for  Full  Forward 
Gear  ...  ....  68 

Finding  the  Positions  of  the  Link  Hanger  and 
of  the  Lifting  Shaft  .  ...  70 

The  Increase  of  Lead  Due  to  Moving  the  Link 
from  Full  to  Mid-Gear  .  .  .  .71 

The  Paths  of  Motion  of  the  Eccentric- Rod  Eye    73 

Diagram  of  the  Port  Openings  for  the  Full 
Gears 76 

The  Port  Openings  for  Cut-off  at  One-Quarter 
Stroke ;  Path  of  Motion  of  Eccentric-Rod  for 
Mid-Gear 77 

The  Port  Openings  for  Mid-Gear  ;  The  Point  of 
Suspension  of  the  Link-Hanger  and  its 
Effect  upon  the  Points  of  Cut-off;  Diagram 
of  Port  Openings  at  Half  and  at  Quarter-Cut- 
off for  Both  Gears  .  ...  78 

Shifting  the  Position  of  the  Saddle-Pin,  and  its 
Effect ;  Equalizing  the  Lead  for  the  Forward 
Gear ;  Finding  the  necessary  Position  of  the 
Eccentrics 79 

The  Effect,  upon  the  Backward  Gear,  of 
Equalizing  the  Lead  for  the  Forward  Gear  81 

Link  Motion  with  Crossed  Rods ;  Finding  the 
Positions  of  the  Parts  .  .  .82 

The  Variation  of  Lead  in  Crossed  Rods ; 
Equalizing  the  Lead  with  Crossed  Rods  .  83 

Link  Motion  with  Allen  Valve         .        .        .84 

Valve  Positions;  Port  Openings  for  Quarter 
Cut-off  given  by  the  Allen  Valve  ;  The  In- 
crease of  Lead  with  the  Allen  Valve ;  Port 
Openings  at  Mid-Gear  with  the  Allen  Valve  85 

Port  Openings  at  Mid-Gear  with  the  Allen 
Valve ;  Gooch's  Link  Motion  .  .  .86 

Finding  the  Positions  of  the  Parts  of  Gooch's 
Link  Motion 87 

The  Points  of  Cut-off,  and  the  Lead  of  the 
Gooch  Link  Motion  .  88 


CHAPTER  IV. 

LINK   MOTIONS   WITH    ROCK   SHAFT. 

The  Offset  of  the  Rocker-arm  .        .        .89 

Finding  the   Positions  of  the  Eccentrics  for 

Link  Motions  with  Rock -Shaft      .        .         .90 
Finding  the  Positions  of  the  Rocker-arms        .     91 
The  Positions  of  the  Parts  when  the  Link  is  in 
Full  Gear ;  The  Positions  when  the  Link  is 
in  Mid-Gear  .  .    92 


CONTENTS. 


ix 


PAGE 

The  Increase  of  Lead  due  to  Moving  the  Link 
1'roni  Full  (.tear  towards  Mid  dear  when  a 
l>'"--k-Shaft  is  Employed  ;  The  Points  of  Sus- 
pension of  the  1. ink-Hanger  .  .  .93 

Finding  the  Positions  of  the  Lifting-Shaft        .     1)4 

Diagrams  of  the  Port  Opening-  of  Link  Motion 
with  Rock-Shaft  in  full  (Jeur.  for  Cut-off'  at 
Half-Stroke  and  for  Mid-Gear  •  .  .95 

Equalizing  the  Points  of  Cut-Oil',  l>y  Shifting 
the  Point  of  Link-Hansrer  Suspension  .  06 

The  KilVetof*  living  the  Valve  Over-Travel        .     '.'7 

•am  of  Port  Openings  when  the  Valve  has 
Over-Travel;  Equalizing  tin'  Points  of  Cut- 
On"  l»v  making  the  Steam  Ports  of  Different 

Widths 98 

'd  of  Finding  the  Amount  of  Variation  of 
Steam  Port  Width  Necessary  to  Equalize  the 
Points  of  Cut-Oil' <)!» 

Link  Motion  with  one  Eccentric  only;  Steam 
Reversing  dears  !()•_' 

Modified  Arrangements  of  Link  Motion  .   Id:; 

Steam  Reversing  dears  ....  1()4 

Bteam  Reversing  Gears  with  Cataract      .        .  105 

Steam  Reversing  Gear  for  Locomotives  .   KM> 


CHAPTER  V. 

ADJrsTAIll.K   CUT-OFF    ENGINES. 

Adjustable  Cut-off  Engine         ....  108 

The  Meyer  Cut  off    .         .  ...   109 

Mever's  Cut-off'  Valve  compared  with  the  Com- 
mon I)  Slide- Valve 110 

The  Action  of  a  Meyer  Cut-off          .         .         .111 

Port  Openings  of  the  Meyer  Cut-off'  in  Com- 
parison with  that  of  Common  Slide- Valves  .  112 

The  Positions  of  the  Parts  in  a  Meyer  Cut-off 
Valve  Motion 113 

The  Limits  of  Eccentric  Position  in  a  Meyer 
Cut-off';  The  Wire-Drawing  at  Late  Points 
of  Cut-off  with  Meyer's  Cut-off;  Diagram  of 
Port  Openings 114 

Equalizing  the  Points  of  Cut-off  with  a  Meyer 
Valve  Motion 115 

The  Limit  of  Eccentric  Position  to  avoid  a 
lit  opening  of  the  Port  ....  ll(i 

Diagram  of  Early  Points  of  Cut-off  with 
Meyer'a  Valves  ;  Varying  the  amount  of  Lap 
with  Meyer's  Cut-off"  Valves  .  .  .117 

Port  Openings,  for  i,  i,  i  and  i  Stroke,  with  a 
Meyer's  Cut-off 118 

Varving  the  Points  of  Cut-off,  by  Moving  the 

Cut-off  Valves  apart  .  '  .  .  .120 


PAGE 
Position  of  Eccentric  for  the  Latest  Point  of 

Cut-off' 121 

Finding  the  Positions  of  the  Valves  Necessary 
for  Cutting  Off'  at  all  Points  between  Given 
Limits  ;   Finding  the  Necessary  Amount  of 
Cut-off  Lap  .        .        .        .        .        .122 

Equalizing  the  Points  of  Cut-off,  by  Moving 
one  Cut-off'  Valve  more  than  the  other; 
Diagrams  Showing  the  Variation  in  the 
Points  of  Cut-off  for  the  two  Strokes 


The  Effect  of  increasing  the  Travel  of  the  Cut- 
off Valve  

Diagram  of  Port  Opening  when  the  Cut-off 
Valves  have  Over-Travel  .... 

Griddle  Valves  or  Multi-Ported  Valves;  The 
Reason  for  Making  the  Cut-off  Valve  Ports 
Wider  than  those  in  the  back  of  the  Main 
Valve 


123 

124 
125 


126 


Investigating  the  Action  of  Griddle  Cut-off 
Valves  127 

Find  ing  the  Positions  of  the  Parts  ;  The  Griddle 
Valves  to  Cut-off'  at  a  Given  Point  in  the 
Stroke 128 

Port  Openings  with  Griddle  Valve  .        .  129 

The  Effect  of  Increasing  the  Travel  of  the  Main 
Valve;  Finding  the  Amount  the  Main  Valve 
Travel  must  be  Increased  to  Vary  the  Point 
of  Cut-off  ....'.  .130 

Diagrams  of  Port  Openings  with  Main  Valve 
Travel  Increased  ....  131 

Separate  Main  and  Cut-off  Valves;  Moving 
the  Cut-off  Valves  apart  to  Vary  the  Point 
ofCut-off 133 

Gonzenbaeli's  Cut-off'  Valve;  Varying  the 
Point  of  Cut-off'  by  Reducing  the  Valve 
Travel ;  The  Extreme  Positions  of  the 
Valves ;  The  Ranges  of  Cut-off  .  .  .134 

Finding  the  Limits  of  the  Range  of  Cut-off' 
with  Gonzenbaeli's  Valve  ;  Diagrams  of  Port 
Openings 135 

The  Effect  of  Widening  the  Cut-off  Valve 
Ports  in  the  Gonzenbach  Valve;  Finding  the 
Positions  of  the  Eccentrics  for  a  Given  Point 
of  Cut-off  with  donzenbach's  Valve  .  .136 

Diagrams  of  Port  Openings  for  various  Points 
of  Cut-off  with  Gonzenbach's  Valve  .  .  137 


CHAPTER  VI. 

VARYING    THE    POINT  OF  CUT-OFF  BY   SHIFTING   THE 
ECCENTRIC   ACROSS   THE   CKANK-SHAFT. 

To  find  the  Position  in  which  the  Eccentric 


*^ 


CONTENTS. 


PAGE 

must  be  Shifted  across  the  Shaft ;  The  Varia- 
tion of  Valve  Lead  due  to  Shifting  the  Ec- 
centric across  the  Shaft  ....  138 

Modification  of  Valve  Lead  due  to  Shifting; 
The  Point  of  Suspension  of  the  Eccentric 
Hanger 140 

Finding  the  Piston  Position  for  a  Given  Posi- 
tion of  Eccentric  141 

Finding  the  Maximum  Port  Opening  for  a 
Given  Position  of  Eccentric  .  .  .  142 

The  Variation  of  the  Point  of  Admission 
when  the  Valve  is  given  Lead  .  .  .  143 


CHAPTER  VII. 

FXAMPLES  FROM  PRACTICE — AUTOMATIC   CUT-OFF 
ENGINES. 

Advantages  of  the  Automatic  Cut-off  Engine  144 

The  Porter- Allen  Engine 145 

The  Eccentric  Link  and  Wrist  Motion  .         .147 

The  Cylinder  and  Valves         ....  148 

The  Construction  and  Action  of  the  Admis- 
sion Valves 149 

Position  of  the  Parts  at  the  Beginning  of  the 
Stroke .  150 

Position  of  Crank.  Eccentric  and  Link  when 
the  Lead  is  set  for  the  Head  End  Port  .  151 

Finding  the  Position  the  Crank  must  stand 
in  when  the  Lead  is  set:  Position  of  the 
Valve  Gear  when  the  Head-End  Port  is 
Full  Open  ...  .  .152 

Position  of  the  Valve  Gear  when  the  Valve 
is  at  the  End  of  its  Travel  for  the  Head- 
End  Port;  Position  of  the  Valve  Gear 
when  the  Cut-Off  Occurs  at  the  Head-End  153 

Position  of  the  Valve  Gear  when  the  Lead  is 
set  for  the  Crank-End 154 

Position  of  the  Parts  when  the  Crank  is  on 
the  Dead  Centre  on  the  Crank-End  .  .  155 

Position  of  the  Parts  when  the  Valve  is  at  the 
End  of  its  Travel  at  the  Crank-End  Port ; 
Increased  Port  Opening  for  the  Crank-End 
Port;  Diagram  of  the  Port  Openings  for  Cut- 
Off  at  Half  and  Quarter-Stroke  .  .  .156 

Variation  of  Piston  Velocity  when  coming  to 
Rest  at  the  two  Ends  of  the  Stroke  .  .  157 

Uniformity  of  Fly-Wheel  Velocity ;  Unequal 
Lead  as  a  Means  of  Counter  Balancing ; 
Proportioning  the  Parts  of  the  Valve  Motion  159 

The  Buckeye  Engine;  Construction  of  the 
Cylinder  and  Valves  .  .  .  .  .160 

Tlie  Buckeye  Valve  Balancing  Mechanism      .   161 


PAGE 

The  Buckeye  Valve  Motion  ....  162 
Tracing  the  Movements  of  the  Valve  Motion  .  166 
Positions  of  the  Eccentrics,  Etc. ;  The  Latest 

Points  of  Cut-Off 168 

Tracing  the  Motion  for  the  Cut-Off  at  Quarter- 
Stroke  170 

The  Compression ;  Diagram  of  Port  Openings 
for  Cut-Off  at  the  Latest  Point,  and  for  Cut- 
Off  at  Quarter-Stroke ;  The  Construction  of 

the  Governor 171 

The  Adjustment  of  the  Governor  .  .  .  172 
The  Action  of  the  Auxiliary  Springs  in  the 

Buck  eye  Governor 173 

Diagram  Illustrating  Speed  Regulation    .         .  174 
The  Armington-Sims   Engine;   The  Cylinder 
and  Valve;  The   Admission;  Exhaust  and 

Compression 175 

The  Governor  Construction       ....  176 
The  Positions  of  the  Eccentrics        .         .         .  177 
Diagrams  for  Finding  the  Eccentric  Position 
for  a  Given  Point  of  Cut-Off         .         .         .179 

Proportioning  the  Valve 181 

Diagrams  of  the  Port  Openings  when  Cutting 

Off  at  T7n,  \  and  J  Stroke       .         .         .         .182 
The  Straight  Line  Engine         .  .  184 

Construction  of  the  Cylinder,  the  Piston  and 

the  Valve       . 186 

The  Governor  Mechanism  ....  187 
The  Construction  and  Nature  of  the  Valve 

Motion  .         .  188 

The    Anti-Friction    Joints;    The  Rock-Shaft 

Construction 189 

The  Different  Positions  of  the  Valve  ;  Equaliz- 
ing the  Wear  of  the  Valve  ;  The  Method  of 
Balancing  the  Valve  .  .  .  .  190 

The  Method  of  Equalizing  the  Points  of  Cut- 
Off;    Tracing    the    Motion   of    the    Parts; 
Finding  the  Position  of  the  Rock-Shaft        .  191 
Tracing  the  Movement  of  the  Eccentric  and 
Valve ;  Harmonizing  the  Piston  arid  Valve 

Movements 192 

Proportioning  the  Port  Openings  to  the  Piston 

Motion    ...  .  194 

The  Construction  of  the  Cross-Head;  The  Ide 

Engine .196 

Construction  of  the  IdeValve;  Construction  of 

the  Ide  Cross-Head  .  .  199 

The  Construction  of  the  Governor  .  .  .  200 
The  Action  of  the  Governing  Mechanism  .  201 
The  Admission  ;  Finding  the  Positions  of  the 

Various  Parts,  and  Tracing  their  Movements  202 
Adjustment  of  the  Ide  Valve  Gear  when  Lead 
is  given 205 


CONTENTS. 


xl 


PAGE 

The  Weetinghonse  Engine        .       .        .        .  2<Mi 

The  Valve  (icar  of  tin-  Westinghouse  Engine  .   I'1  is 

The  Governor  of  the  Weatinghouae  Engine  .  2<i'.) 
The  Multi-Cylinder  Engine  .  .  .  .-11 
The  James  and  Wardrope  Engine  .  .  .  -I- 

The  N.  V.  Safety  Steam  Power  Co.'s  Engine  .  21  t 
The  Ball  Automatic  Cat-Off  Engine  .  .214 

Eccentric  ('(instruction  of  the  Hall  Engine  .  215 
Valve  Construction  of  the  Hall  Engine  .  .  216 
The  Dexter  Automatic  Cut-Off  .  .  .217 
Construction  of  the  Valve  in  the  Dexter 

Engine 218 

Construction  of  the  Dexter  Governor      .       .220 
The  Corliss   Automatic  Cut-oil'   Engine;   The 
Reynolds  Corliss  Engine;  The  Valve  dear; 

The  Admission 22.'! 

The  Governor  Connection  ;  The  Construction 

of  the  Valves 227 

Position  of  the  Parts  when  the  Crank  is  on  the 
Dead   Centre  and   the  Piston  at  the  Crank 
End         ...  ....  22s 

Varving  the  Engine  Speed        ....  229 

The"  Greene  Automatic  Cut-Oil'  Engine;  The 

Harris  Corliss  Engine;  The  Fishkill  Engine  231 
The  Whoelork  Automatic  Cut-Off  Engine       .  234 

The  Valve  Ge:ir 235 

The  Construction  of  the  Dash  Pot ;  The  Com- 
pression ;   Equalizing  the  Points  of  Cut-Off.  236 
The  Twiss  Engine 237 


CHAPTER  VIII. 

THE  COMPOfXn    KXGIXE. 

The    Principles   of    the   Compound    Engine; 

Principal  Methods  of  Compounding  .  .  239 
Arrangement  of  Engines  of  Ocean  Steamships  240 
Kaivot's  Compound  Engine  ....  241 

CHAPTER  IX. 

THE   CONDENSING    ENGINE. 

Object  of  employing  a  Condenser  ;  Classifica- 
tion of  Condensers 244 

The  Bulkley  Injector  Condenser  .  .  .  245 
Application  of  Bulkley's  Injector  Condenser  .  247 
Knowles'  Independent  Jet  Condenser  .  .248 
Bulklcy's  Injector  Condenser  as  arranged  for 

Natural  Water  Supply 24!» 

Application  of  the  Knowles  Condenser    .         .  250 
Knowles  Condenser  with  Safety  Valve     .         .  251 
Surface   Condenser;    Wheeler's    Independent 
Surface  Condenser          .  .        .         .  252 


PAGIl 

Bulkley's  Independent  Injector  Condenser; 
The  Reynolds  Condenser;  The  Heater  of 
Reynolds' Condenser 255 

Construction  of  Reynolds'  Condenser       .        .  259 

CHAPTER  X. 

COMPOUND   CONDENSING    AND   TRIPLE    EXPANSION 
STATIONARY    KM; INKS. 

The  Worthington  Compound  '  Condensing 
Engine 260 

Triple  Expansion  Stationary  Engines;  A 
Triple  Expansion  Engine  for  Driving  Mills  .  266 

Example  of  a  Triple  Expansion  Stationary 
Engine  in  which  the  Cylinders  are  arranged 
one  above  the  other 270 

Set  of  Diagrams  of  the  Above  Engine     .        .  274 

CHAPTER  XI. 

THE    MARINE     ENGINE. 

Application  of  the  Term  "  Marine  Engine  ;  " 
Displacement  of  Compound  Marine  Engines 
by  Triple  Expansion  Engines;  Causes  of 
the  Greater  Economy  of  Fuel  Consumption 
with  Triple  Expansion  Engines  .  .  .  275 

Example  of  a  Compound  Condensing  Marine 
Engine ;  Small  Marine  Engine  with  Hand 
Reversing  Gear 276 

Marine  Engine  for  Coasting  Vessels;  Com- 
pound Condensing  Marine  Engine  for  an 
Ocean-going  Steamship  ....  279 

Engine  with  Joy  Valve  dear    .         .  .282 

Engine  with  Bryce  Douglass's  Valve  Gear; 
Examples  of  Triple  Expansion  Engines  .  285 

Engines  of  the  S.  S.  Mariposa;  Morton's 
Patent  Valve  Gear ;  Triple  Expansion  En- 
gines of  the  Steam  Yacht  Mira  .  .  .  287 

Triple  Expansion  Engines  of  the  Steamship 
Meteor;  Research  Committee  on  Marine 
Engine  Trials — Report  upon  Trials  of  theS. 
S.  Meteor  from  a  Paper  read  before  the  In- 
stitution of  Mechanical  Engineers,  by  Pro- 
fessor Alexander  B.  W.  Kennedy  ;  Descrip- 
tion of  the  Meteor 296 

Engines;  Boilers;  Object  of  Trial;  Coal  Meas- 
urement . 298 

Analysis  of  the  Coal,  by  Mr.  C.  J.  Wilson ; 
Furnace  Gnses  ;  Feed  Water  Measurement  .  299 

Power  Measurement;  General  Conditions; 
Results;  Duration  of  Trial ;  Fuel;  Analysis 
of  Furnace  Gases 300 

Feed  Water ;  Speed  ;  Pressures,  etc. ;  Power    .  301 


Xll 


CONTENTS. 


PAGE 

Boiler  Efficiencies ;  Engine  Efficiencies ;  Total 
Efficiency  ;  Steam  by  Indicator  Diagrams  302 

Proportion  of  Steam  accounted  for  by  Indi- 
cator Diagrams  .  ....  303 

Coal  Consumption;  Speed  of  Vessels;  Supple- 
mentary Trial 304 

Supplementary  Trial  at  Full  Power  with 
Forced  Draught 306 

Observers  ........  308 

Quadruple  Expansion  Engines        .        .        .  309 


CHAPTER  XII. 

VARIOUS    APPLICATIONS   OF   THE    STKAM    ENGINE. 

The  Traction  Engine;  The  Frick  Traction 
Engine 312 

The  Boiler  and  Reversing  Gear  of  the  Frick 
Traction  Engine 315 

The  Portable  Engine 318 

The  Frick  Company's  Portable  Engine  :  Semi- 
portable  Engine  by  the  Lidgerwood  Manu- 
facturing Company 319 


PAGE 

Colwell's  Engine  for  Sugar  Mills  .  .  .321 
The  Steam  Fire  Engine;  Principal  Classes  of 

Steam  Fire  Engines ;  The  Silsby  Steam  Fire 

Engine 325 

Hoisting  Engines;  Mundy's  Hoisting  Engine  327 
Mundy's  Friction  Drum ;  The  Lidgerwood 

Hoisting  Engine 328 

Robertson's  Semi-Rotary  Engine;  The  Rotary 

Engine  .  ......  329 

Advantages  and  Disadvantages  of  the  Rotarv 

Engine ".331 

Directly  Connected  Engines  ....  333 
Rock  Drilling  Engine  or  Rock  Drill ;  The 

Ingersoll  Eclipse  Rock  Drill.  .  .335 

The  Ingersoll  Air  Compressor  ....  338 
The  Knowles  Steam  Pump  ....  342 
The  Worthington  Steam  Pump  .  .  .  344 
The  Worthington  Pump  as  applied  to  Brewery 

Purposes 346 

The  Gordon  &  Maxwell  Isochronal  Pumping 

Engine 347 


INDEX 


.  351 


MODERN  STEAM  ENGINES. 


C  H  A  I'  T  K  I,'     I 


CLASSIFICATION-  OK  STKAM  EN(;INKS THE  COMMON  SLIDE  VALVE  KNOI.VE. 


different  forms  in  which  the  steam  engine 
appears  niny  lie  elnssilied  as  follows: 

..//,  prtsaun  r //.///,,.  in  whic.h  the  steam,  at  what- 
ever pressure  it  may  be  used,  exerts  its  pressure  in  one 
cylinder  only,  and  is  then  exhausted  into  the  atmos- 
phere. 

'/'/'"•  compound  rni/i>te,  in  which  the  steam,  after  having 
been  used  in  one  cylinder,  passes  to  a  second  and,  in 
some  cases  to  a  third  cylinder  where  it  is  used  expan- 
sivoly  before  being  exhausted  into  the  atmosphere. 
"When  the.  steam  expands  in  a  third  cylinder,  the  engine 
is  said  to  have  a  triple  expansion. 

The  condensing  emjine,  in  which  the  steam,  instead  of 
a;  exhausted  into  the  atmosphere,  is  condensed, 
creating  a  vacuum  (or,  more  properly,  a  partial  vacuum) 
on  one  side  of  the  piston,  thus  relieving  it  from  the 
pressure  of  the  atmosphere  which  would  act  to  counter- 
act the  steam  pressure  on  the  other  side. 

Tttf,  compound  condensing  engine,  in  which  the  steam  is 
used  first  in  a  high  pressure  cylinder  recieving  steam 
from  the  boiler,  and  then  in  one  or  more  low  pressure 
cylinders  and  is  finally  condensed,  forming  a  vacuum 
on  the  exhaust  side  of  the  piston. 

In  some  one  of  these  forms  the  steam  engine  appears  i 


in  each  of  its  applications.  Engines  are,  however,  als  > 
designated  to  indicate  the  purposes  for  which  they  are 
used,  as  marine  engines  for  steamships,  locomotives  for 
railways,  portable  engines  for  those  intended  to  be 
moved  from  place  to  place,  stationary  engines,  as  those 
set  upon  permanent  foundations  as  in  factories. 

They  are  further  designated  from  especial  features  in 
the  design,  as  beam  engines,  where  the  piston  delivers 
its  power  to  a  beam,  side  lever  engines,  where  the  beam 
or  beams  are  at  the  side  of  the  cylinder  instead  of 
above  or  below  it. 

Oscillating  engines,  in  which  the  cylinder  oscilates 
upon  journals  or  trunnions  in  order  to  avoid  the  use  of 
guide  bars,  and  thus  economize  space. 

Direct  acting  engines,  in  which  the  piston  rod  is  con- 
nected direct  to  the  crank  by  means  of  a  connecting 
rod. 

Vertical  engines  or  horizontal  engines,  according  i<» 
whether  the  cylinder  bore  stands  vertical  or  horizontal, 
and  inclined  engines  when  it  stands  in  neither  of  those 
positions. 

Traction  engines  are  those  employed  to  draw  loads, 
without  the  use  of  rails,  usually  upon  common  roads 
or  highwavs. 


OF  THE 

(UNIVERSITY 


12 


MODERN  STEAM  ESGIXES. 


COMMON  SLIDE   \M.  V~E  EXGINE. 


13 


is  <>!»'  in  which  the  cyl- 
inder stands   vertical    iiinl    the    piston   operates   through 

iwer  cylinder  cover. 

When,  as  in  i '  most  ocean  going  steamships, 

tin-  cylinders  staiicl    in   a  lint'  with    the  crank    shaft,  the 
id    to    1»  •'•  tilt1  cylimlt-rs 

arranged  tandt 

in  which  the  piston  motion  is 

in  a  circle  around  the  pi-ton  rod  or  shaft,  or  it  may 
rcvolvf  around  the  shaft  in  some  curve.  It  is.  however. 
attached  direct  to  it-,  rod  '.while  temi+otary 

•'•c  those   in  which  the    pistol!  reciprocates    ill    all 
arc    or   segment    of  a  circle  of  which    the  the 

center. 

vever,    may   be 

further  designated  l>y  the  peculiar  design  or  o]>eration 
of  its  parts;  thus  a  simple  slide  valve  engine  is  one  in 
which  the  admission  of  steam  is  effected  by  a  simple 
j<n  D  valve,  as  it  i-  sometimes 
called. 

A   //'  ne  in   which  the  speed  of  the 

engine  ig  regulated  l>y  a  fly-ball  frovcrnor  which  par- 
tially closes  or  throttles  the  bore  of  the  steam  pii«>,  and 

thus  causes  the  steam  to  enter  the  steam  chest  at  a  re- 
duce.) pressure':  an  action  that  is  termed  tetra  drawing 

A  .  ii    is  one   in  which  the  steam  supply  to 

cylinder   is   piverned  by  a  cut-off  valve  or  valves. 

\\  hen  the   point    in  the  piston   stroke  at  which   the  cut- 

olT  valve  will  act  is  adjustable  by  hand,   the  engine  is 

an  </.//».•.•.  When  the  point  of  cut-off 

"Veriied  by    the    engine    itself,  it   is  an    iiiitmiKitic   cut- 

There   are    also    disc    enyinen,  m   which   the    pistons 

operate    against    a    disc.       J/w///— C/////K//T    ciii/iiii's,    in 

which  a  number  of  cylinders  are  arranged  either  side 

b\  side,  or  with  their    IK  ires   radiating  from  the  engine 

!.  each  taking  steam  at  one  end  only. 

THE    COMMON    SI.IHK    VAI.VK    KXdIXK. 

The  sini]>lest  form  of  high  pressure,  or  non-condens- 
ing engine,  is  the  common   slide  valve  engine,  whose 
is  shown  in  Figs.  1,  2,  3  and  4,  which  rep-- 

•  nt  a     hori/.ontul   stationary   engine.       Fig.    1     ; 


14 


MODERN  STEAM  ENGINES. 


s'Mu  view,  showing  the  guide  liars  and  crank  with  the 
crank  end  of  the  connecting  rod.  Fig.  '2  is  a  view 
from  the  other  side  showing  the  eccentric  and  the  slide 
spindle  and  its  guide  II.  Fig.  3  is  a  top  view  of  the 
engine,  the  cylinder  and  steam  chest  being  shown  cut 


Fig.  5  represents  (removed  from  the  other  parts  of 
the  engine)  a  cylinder  €,  steam-chest  S,  slide  valve  V 
and  a  valve  rod,  or  spindle,  li.  The  cylinder,  C.  is  pro- 
vided with  three  ports  or  openings,  a,  I,  and  c,  the  first 
and  second  of  which  are  called  the  steam  ports,  while  c 


EXHAUST  PIPE 


Kg.  4. 


ia  half  horizontally  so  as  to  expose  the  mechanism, 
and,  as  the  names  of  the  parts  are  marked  upon  them. 
there  is  no  occasion  to  enumerate  them.  It  may  be 
noted,  however,  that  the  bed  plate,  the  connecting  rod 
and  the  eccentric  rod  are  shown  broken  for  convenience 
of  illustration.  In  Fig.  3,  the  crank  is  shown  on  its 
dead  center  and  the  piston,  therefore,  at  the  end  of  the 
stroke,  and  it  is  obvious  that  the  pressure  exerted  upon 
the  piston  by  the  steam  would  have  no  effect  in  moving 
the  engine,  because  the  crank,  connecting  rod  and 
piston  are  in  a  straight  line.  Fig.  4,  however,  shows 
the  parts  in  the  position  they  would  occupy  when  the 
crank  was  at  its  point  of  full  power,  and  it  is  obvious 
that  as  soon  as  the  crank  has  moved  off  its  dead  center 
the  steam  pressure  upon  the  piston,  is  in  a  direction  to 
cause  the  crank  to  revolve  and  drive  the  fly-wheel  whose 
momentum  carries  the  crank  past  its  dead  center. 

The  action  of  the  slide  valve  that  governs  the  admis- 
sion of  the  steam  into,  and  its  exhaust  out  of,  the 
cylinder  may  be  explained  as  follows: 


is  the  exhaust  port.  The  slide  valve,  V,  fits  closely  to 
the  face  where  these  ports  emerge  into  the  steam  chest 
and  is  traversed  to  and  fro  across  them,  the  distance  it 


Fig.   5. 

travels  in  one  stroke  being  called  the  amount  of  the 
valve  travel.  It  is  operated  by  a  rod  R,  or  the  slide 
valve  spindle  as  it  is  termed,  which  receives  motion 


COMMON  SLIDE   r  I/.  VE  ENGINE. 


15 


fi..in  lli.  r«il  shown  in    Fig.  ::.      Now  suppos- 

ing the  crunk  to  be  on  its  dead  center   and  the   piston  in 
jH.sition  it  occupies  in   the  figure  and   the  valve  will 
have    left    port    n  open    to    ;  ml    of   the  leail.   the 

OH!  the  ehe-l  \'.  through  d.  into  tlie 
<lylimlcr.  At  this  time,  port  // is  acting  as  an  exhaust 
port,  the  steam  that  propelled  the  pi-ton  during  the 
previou-  sti-oke  pa.--ing  through  the  valve  exhaust  port 
as  it  may  more  properly  lie  termed) 
and  into  the  cylinder  exhaust  port  <•,  whence  (in  a  high 

llto    the    atmosphere.        Thus 

am  port.  /.  is  acting  as  an  exhaust 

port.      Hut    by  the  time  the  piston  has  reached  the  other 

end    of   the    cylindcr,and     1  -re    completed     its 

the  valve  will    have  moved  so  as  to  leave    //  open 

team    chest    «nd    leave    communication    between 

'    "   and   (through    </)  the    cylinder    exhaust    port   c. 

Jlence   n    and    /-   act    alternately   as    steam    and    exhaust 

port*,  and  win  n  either  of  them  is  admitting  steam  it  is 

'•I.    while   when    it    permits  the   steam 

.1   of    the   cylinder    it    is   called    an   tjcliniixt 

The    action    of    a   slide    valve    may.   within    certain 

limits,  lie  varied  at  will    Iiy   altering  its  proportions  and 

the  amount  of   its  travel   or  sliding  motion.      It  may   lie 

gned  eoas  to  lei   the  .-team  from  the  steam  diet 

-   into   the  cylinder  during  the   whole  of  the  piston 

!;e.  or  so  as  to  doBO  the  steam  port  before  the  piston 

traveled  a   full  stroke,  so  that  after  the  valve  closes 

the  steam     port,    the    steam    already    in    the    cylinder 

expands  and  drives  the  piston   for  the  remainder  of  the 

stroke   without  using  any   more   steam    from    the  steam 

Hi;-  action  i-   called  working   steam  a 
point  in  the  piston   movement  at   which  the  valve 
..m   port   is  called    the  point  of  ettt-O/.      The 
m  that  enters  the  cylinder  while;  the  steam  port  is 
open   is  .  while  from  the  moment   the  steam 

port  doses  and  the  steam  in  the  cylinder  begins  to  ex- 
pand, it  is  no  longer  live  steam  but  expansive  steam. 
r'itr.   'i  represents  the  construction  of  a  valve  to  let 
:a  follow  the  piston  during  full  stroke;  A  and 
C  are  the  cylinder  ports,  and  B  is  the  cylinder  exhaust 
'x'rt:   1)  is  the  valve  exhaust  cavity  and  E  and  F  arc 
The  edges  G  and  H  of  the  valves  are  the 
:u  edges,  because  it  is  their  passage  over   the 


;ve  ports   A    an. I  C    that  admits  the  live  steam  to 

or   CUta    it  off    from    entering     those    ports.       The    inside 

•  1'  the  valve,  as  denoted  by   the  arrows  in  port  I), 


E 


6. 

are  the  •  //,,i//.sV-«///c*  of  the  valve,  liecause  it  is  their 
pas-age  over  the  ports  A  and  C  that  opens  or  closes 
them  as  exhaust  ports.  The  total  width  of  the  valve, 
from  edge  (I  to  ed^c1  II.  i-  in  this  case  (to  let  live  steam 
follow  full  stroke)  made  to  just  cover  the  two  ports  A. 
0  that  when  the  valve  is  in  the  middle  of  its  travel 
(as  it  is  shown  to  bo  in  the  cut),  no  steam  can  get  into 
or  out  of  the  passages  A.  C.  The  width  of  the  valve 
exhaust  port  I)  (that  is,  the  distance  between  its  exhaust 
edges)  is,  in  this  case,  made  to  extend  as  nearly  across 
the  two  bridges  E,  F,  as  is  compatible  with  covering 
them  sufficiently  to  prevent  the  passage  of  steam  from 
cither  C  or  A  into  D  and  E,  when  (as  in  the  cut)  the 
valve  is  in  the  middle  of  its  travel.  But  if  the  valve 
be  moved  from  this  position,  in  either  direction,  both 
ports  will  be  put  in  action,  one  as  a  steam  and  the  other 
as  an  exhaust  port.  Thus  in  Fig.  7,  the  valve  having 


traveled  in  the  direction  of  the  arrow,  port  A  is  open, 
so  that  steam  may  enter  the  cylinder  driving  the  piston 
in  the  direction  of  the  arrow  z.  During  this  valve  move- 
ment, the  edge  e,  of  the  port  C  has,  in  conjunction  with 
edge /of  the  valve,  afforded  an  opening  for  the  steam 
in  C  to  escape,  and  the  edge  e  is,  therefore,  called  the 
exhaust  edge  of  the  port.  On  the  other  hand,  edge  y 


1G 


MODERN  STEAM  ENGINES. 


of  port  A  lias,  in  conjunction  with  edge  '/  of  the  valve, 
afforded  ingress  to  steam  at  A.  Hence  edge  <j  is  the 
steam  edge  of  the  port. 

By  the  time  the  piston  lias  arrived  at  the  end  of  the 
stroke,  denoted  by  x,  the  valve,  will  have  traveled  back 
to  the  position  shown  in  Fig.  <>.  A\rhen  the  piston  has 
made  one-half  its  return  stroke,  the  valve  will  be  in  the 
position  shown  in  Fig.  8;  both  piston  ami  valve  moving 
2 


Fiy.   8. 

in  the  same  direction,  as  denoted  by  arrows  y  and  z. 
At  this  time,  port  C  will  be  full  open  as  a  steam  port, 
and  port  A  full  open  as  an  exhaust  port,  the  steam 
passing  from  A  into  B,  as  denoted  by  the  curved  arrow. 
These  respective  valve  and  piston  movements  being 
repeated,  the  piston  is  driven  to  and  fro  in  the  cylinder 
by  steam  on  one  side  of  it,  while  that  which  drove  it  on 
the  previous  stroke  is  exhausted,  through  B,  into  the 
atmosphere. 

STKAM    LAP. 

To  enable  a  slide  valve  to  cut  off  the  steam  supply  to 
the  cylinder  before  the  piston  has  completed  its  stroke, 
and  thus  cause  the  steam,  admitted  before  the  cut-off 
occurred,  to  work  expansively  during  the  remainder  of 
the  piston  stroke,  what  is  termed  steam  lap  is  given  to 
the  valve,  as  shown  in  Fig.  9.  Here  the  steam  edges, 


ff. 


Fig.   9. 

G  and  H,  of  the  valve,  instead  of  barely  covering  the 
ports  A  and  C,  as  in  Fig.  6,  are  prolonged  over  them 


by  the  distances  I  and  J,  respectively,  and  the  amount 
to  which  this  prolongation  or  overlapping  extends  (the 
valve  being  in  the  middle  of  its  travel)  is  called  the 
steam  lap.  The  measurement  of  this  lap  is  designated 
in  terms  of  its  length  on  each  side.  Thus  if  I,  and  J 
measure  an  inch  each,  the  valve  has  an  inch  of  steam 
lap  on  each  end. 

The  Jiji  of  the  valve  means  that  part  of  the  flange, 
at  each  end  of  the  valve,  that  covers  the  steam  port  and 
extends  beyond  it;  thus,  in  Fig.  0,  the  lip,  at  one  end, 
is  from  the  steam  edge  H  to  the  left-hand  edge  of  the 
port  C,  and  at  the  other  end  of  the  valve  it  is  that  part 
from  the  edge  G  to  the  right-hand  edge  of  port  A. 

The  action  of  steam  lap.  in  cutting  off  the  steam 
supply,  is  shown  in  Fig.  10,  in  which  the  valve  and 


D 


10. 


piston  moving  in  the  direction  denoted  by  the  arrows, 
the  steam  on  the  side  P  of  the  piston  is  enclosed  by  the 
walls  of  the  cylinder,  the  face  P  of  the  piston,  and  the 
valve  face  at  a;  the  resulting  expansion  of  the  steam 
continuing  until  the  edge  c  of  the  valve  meets  the  edge 
of  the  port  a,  at  which  time  the  piston  will  have  nearly 
completed  its  stroke. 

Now,  whether  a  valve?  has  a  steam  lap  or  not,  it  is 
evidently  essential  that  when  the  piston  is  at  either  end 
of  its  stroke,  the  valve  must  be  in  a  position  to  admit 
steam  to  one  end  of  the  cylinder  and  permit  it  to  escape 
from  the  other  end.  Furthermore  it  is  found  necessary 
(in  order  to  prevent  the  parts  from  reversing  their  direc- 
tion of  motion  with  a  /»/»;/</,  kimrk,  or  llnun/i)  to  prevent 
all  the  steam  from  being  exhausted,  a  certain  proportion 
being  enclosed  in  the  cylinder  before  the  piston  readies 
the  end  of  its  stroke,  so  that  the  piston,  during  the  latter 
part  of  each  stroke,  has,  on  one  side,  a  steam  pressure 
forcing  it  ahead,  while,  on  the  other  side,  it  is  compress- 


ECCENTRIC  THROW-    ANGULAR  ADVANCE-   VALVE  I.I 


17 


>rne  of  the   steam   that  would  otherwise  exhaust 

thus    prevented     from    r-<'a]>inur.    ftCtS 
D  on  the  advancing   piston  ami  causes  the  recipro- 
ihc    piston   and    its  rod,    the    crosshead 
and   the  Connecting  rod)  t  their  iiH.ii.ms  easily. 

Tills     is     termed  ,//'/    or     (  .      and      till1 

iiniount  ne.-.  «   the  aliovc    purpose   depends  upon 

.  •  •!'   the   engine  and    cither   considerations    that 
will  appear  hereafter. 

For  the  same -purpose,  and  also  to  fill  the  steam  port 
with  live  steam  at  a  pressure  nearly  e<|iial  to  that  in  the 
steam  chest,  the  valve  is  given  what  is  called  lead, 
which  will  lie  expla;  Mtly. 

The  valve  is  operated  l>y  an  eccentric  which  is  driven 
by  the  crank  shaft,  axle,  or  main  shaft  of  the  engine. 

The  thniir  of  an  eccentric   is  the  amount   its  center  is 
distant   from   the   axis  of  its   Lore   or  from   that 
shaft  by  which  it  is  revolved,  and  a  straight  line  passinjr 
through    these    two    centers   is   termed    the    '///" 
Thus,  in  Fig.  11.    A    represents  the  center  of  the  bore 


11. 


of  tn  eccentric,  and  B  the  center  of  the  eccentric,  hence 
the  radius  tnmi  A  to  B  is  the  throw  of  the  eccentric — 
which  eepials  one-half  the  travel  of  the  valve.  Thus  if 
the  eccentric  be  moved  through  one-half  a  revolution 
on  its  axis  A.  its  center  B  would  move  in  the  dotted 
an-  ( ',.  and  the  distance  it  would  move  its  rod  would  be 
equal  to  the  radius  E,  F,  or  twice  the  distance  A,  1!. 
The  thio\v  line  A,  B,  is,  for  convenience,  taken  to 


represent  the  position  of  the'  eccentric,  and  the  throw- 
line  of  the  crank  is  taken  to  represent  the  position  of 
the  crank.  \Vhen  the  eccentric  throw-line  moves  in 
advance  of  the  crank  in  the  path  of  revolution,  it  is  said 
'./  the  crank,  and  it  is  olivious  that,  in  this  case, 
the  crank  and  eccentric'  will,  at  the'  beginning  of  the 
piston  stroke'  (the  crank  having  moved  \>:i>t  either  of 
itsdead  centers)  move  in  the  same  direction,  whereas, 
when  the  eccentric  follows  the  crank,  it  will  (at  the 
beginning  of  the  piston  stroke)  move  in  the  opposite 
direction  to  the  crank,  the  word  //iredion  referring  to 
ritrht.  and  left,  and  not  to  the  path  of  revolution. 
In  a  simple  slide  valve  engine,  such  as  in  Figs.  1,  '1, 
3,  and  4,  the  eccentric  leads  the  crank. 

VAI.VK    I. KAIL 

The  lead  of  a  valve  is  the  amount  to  which  it  has 
opened  the  steam  port  when  the  piston  is  on  the  dead 
center.  Lead  is  given  to  a  valve  by  advancing  the 
position  of  the  eccentric  with  relation  to  the  crank.  If 
a  valve  has  neither  lap  nor  lead,  the  throw-line  of  the 
eccentric  will  stand  at  a  right  angle  to  the  throw-line  of 
the  crank,  as  shown  in  Fig.  12,  in  which  S  represents  a 
steam  chest.  V  the  valve  broken  away  at  the  bottom  to 
expose  the  cylinder  ports,  P  the  direction  of  crank  revo- 
lution. A  the  throw-line  of  the  crank,  and  B  the  throw- 
line  of  the  eccentric.  To  give  the  valve  lead,  it  v/ould 
be  necessary  to  move  the  eccentric  forward  on  tin- 
shaft  until  the  valve  opened  the  port  to  the  required 
amount,  in  which  case  its  throw-line  would  stand  at  an 
obtuse  angle  to  A  instead  of  at  a  right  angle. 

To  reverse  the  direction  of  crank  revolution,  all  that 
is  necessary  is  to  move  the  eccentric  on  the  shaft  until 
its  throw-line  stands  at  E,  or  still  further  according  to 
the  amount  of  the  lead  required.  When  the  eccentric 
rod  is  attached  direct  to  the  slide  valve  spindle,  the 
eccentric  throw-line  always  stands  in  advance  of  that 
of  the  crank,  no  matter  in  which  direction  the  crank  is 
to  revolve.  This  is  shown  in  Fig.  12,  in  which  (motion 
being  supposed  to  commence  from  the  dead  center)  it 
is  obvious  that  B  will  pass  the  other  dead  center  in 
advance  of  the  crank.  The  amount  to  which  the  eccen- 
tric throw-line  is  set  forward,  or  in  advance  of  the  crank 
throw-line,  is  termed  its  angular  advance,  and  is  meas- 
ured in  degrees  of  angle;  in  the  upper  half  of  Fig.  12 


18 


MODKRX  ,S77-;,1J/  EXCIXMS. 


it  is   shown  at  a  right  angle,  or  an  angle  of  90°  to  the 
crank. 

The  amount  to  which  an  eccentric  requires  angular 
advance  increases  in  proportion  as  the  valve  is  given 
steam  lap  and  lead.  Thus  in  the  lower  half  of  Fig.  1 2 
is  a  valve  having  steam  lap  and  lead.  The  eccentric 
throw-line  is  seen  to  be  at  an  angle  of  120°  instead  of 
at  an  angle  of  90°,  as  in  the  upper  half  of  the  figure. 
The  positions  of  the  valves  are,  so  far  as  the  steam  port 
at  end  S  is  concerned,  the  same  in  both  figures,  except 


In  Fig.  13  is  shown  a  valve  luiving  exhaust  lap,  the 
width  at  P  being  less  than  that  at  Q,  and  the  amount  of 
exhaust  lap  being  denoted  by  K  or  by  L.  The  manner 
in  which  exhaust  lap  operates  is  shown  in  Fig.  14, 
where  the  piston,  moving  in  the  direction  of  /,  is  near 
the  end  of  its  stroke;  the  valve,  moving  in  the  direction 
of  d,  is  about  to  open  port  a  as  an  exhaust  port.  Sup- 
pose then  that  the  valve  cavity  D  has  exhaust  lap  added, 
as  denoted  by  the  dotted  line,  then  the  valve,  will  re- 
quire to  move  still  further  before  the  port  a  opens  to  the 


12. 


that,  in  the  lower  half  of  the  figure,  the  valve  is  shown 
to  have  a  slight  lead. 

The  exhaust  lap  of  a  valve  is  the  amount  to  which  its 
exhaust  cavity  or  port  (when  in  its  mid  position  over 
the  cylinder  ports)  covers  the  cylinder  port  bridges. 


Fig.   13. 


exhaust,  and  during  this  valve  movement  a  certain 
amount  of  piston  movement  will  occur,  and  to  this 
amount  the  steam  will  have  been  detained  in  the  cylin- 
der by  reason  of  the  exhaust  lap. 

Thus,  then,  the  effect  of  lead  and  of  exhaust  lap  is  in 


1-1. 


CUSHION— CLEARANCE— VALVE  TRA 


19 


tin1  same1  din  m   port   to  be 

•I  with  strain  by  the  time  the  jiiston  reaches  the  ciul 
of   il  Rut    the  steam   admitted   by    the    Valve 

lead   is  live  steam   drawn   from   the   steam   chest,  while 
that  enclosed  by  exhaust   lap  is  saved  from  the  exhaust, 
or,  in  other  words,  is  a   part  of  tin-  steam   admitted    to 
the  cylinder  on  the  previous  piston  stroke.      Both,  how- 
ever,  obviously  serve  to  arrest   the  piston  motion  at  or 
towards  the  end  of   the  stroke,  and.  therefore,  cause  the 
reciprocating  parti  of  the    engine.    .'.  >'..  the   piston   and 
foil,  the   cross-head    a'nd   the  connecting   rod.  to   re- 
B   their  direction  of  motion  easily  or  without   shock, 
which  results  because  the  p res-ure  on  the  piston,  due  to 
ioning,  reverses   the  direction  of   contact  of   the 
join  ..re  the   piston   reverses  its  motion.     Thus 

when  the  piston  is  pulling  the  connecting  rod,  its   i 

is  transferred  through  the  half  brass  (on  tho  cross- 
head  and  crank  pin  respectively)  that  is  furthest  from 
the  cylinder,  while  when  the  piston  is  pushing  the  con- 
necting i'od.  its  pressure  is  transferred  through  tho  half 
brasses  that  are  nearest  1o  the  cylinder.  Now  if  the 
transfer  of  pressure  or  contact  from  ono  half  brass  to 
the  other  takes  place  at  the  extreme  end  of  the  stroke, 
and  coincident  with  the  admission  of  steam,  the  motion 
ie  jiiston.  cro.---liead  and  connecting  rod  will  be  re- 
.ddenly  and  violently,  especially  if  there  lie  any 
jilay  or  loosene-s  between  the  connecting  rod  brasses 
and  the  crank  jrin  or  cross-head  journals.  But  when 
cushioning  is  resorted  to.  either  by  means  of  lead  or 
exhaust  lap.  the  contact  between  the  brasses  and  their 
journals  is  transferred  from  one  brass  to  the  other  while 
the  jiiston  is  moving  in  the  one  direction  and  is  just 
completing  its  stroke,  so  that  by  the  time  it  has  com- 
pleted it.  the  brass  and  journal  contact  ia  on  the  proper 
;'or  the  ensuing  stroke. 

CLEARANCE. 

•mii'-r  in  a  valve  is  the  amount  to  which  its  ex- 
haust cavity  is  wider  than  the  extreme  width  of  the 
bridges,  leaving  all  the  ports  open  when  the  valve  is  in 
mid-position  as  at   A,  in   Fig.  15.     "With  no  steam  lap, 
ranee  permits  the  steam  to  escape  when  the  port  is 
:ed  for  admission,  as  at  B.     This  may  be    avoided 
by  giving  more  lap  than  clearance.     Clearance  reduces 
tin-  compression,  and  prevents  the   engine  from  thump- 
3 


ing  when  the  valve  has  a  maximum  of  steam  lap.  In 
position  ( '.  for  example,  the  dotted  half  circle  represents 
no  clearance,  and  it  is  seen  that  the  compression  for  port 


LJ 

Pig.  15. 

c,  is  delayed  by  the  clearance  during  a  portion  of  valve 
movement,  represented  by  the  distance  between  the 
edge  of  tho  valve  cavity  and  the  dotted  half  circle. 

VALVE    TRAVEL. 

Tho  travel  of  a  valve  is  the  amount  of  its  motion 
over  or  across  the  steam  ports,  and  is  varied  to  suit  the 
proportions  of  the  valve.  The  manner  in  which  a  valve 
will  admit  steam  to  the  cylinder,  and  the  relation  of 
such  admission  to  the  piston  movement,  is  governed  by 
the  steam  lap,  the  lead,  and  the  travel  of  the  valve, 
while  tin:  manner  in  which  the  steam  will  be  exhausted 
from  the  cylinder  and  its  relation  to  the  piston  move- 
ment is  governed  by  the  valve  exhaust  port,  the  lead, 
and  the  valve  travel.  NOAV  the  least  variation  in  either 
the  lap  or  travel  of  a  valve  has  a  marked  effect  upon 
the  disposition  of  the  steam  to  the  cylinder,  and  the 
combination  of  varying  proportions  that  may  be  given 
to  a  valve  without  varying  tho  dimensions  of  the  cylin- 
der ports  are  so  numerous  that  only  the  general  effects 
of  each  of  the  elements  (as  steam  lap,  exhaust  lap,  travel 
and  lead)  will  be  at  present  considered. 

In  proportion  ;&s  steam  lap  is  given  to  a  valve  its 
travel  and,  therefore,  the  eccentric  throw  must  be  in- 
creased in  order  that  tho  port  may  open  fully  as  a  steam 
port.  But  the  width  of  the  bridges  must  be  sufficient 
to  prevent  the  valve  from  moving  so  far  over  the  ports 
as  to  leave  loss  opening  at  the  cylinder  port  P,  Fig.  16, 
than  there  is  at  the  exhaust  port  (as  B  in  the  figure)  or 
otherwise  tho  cylinder  exhaust  port  will  be  cramped,  as 
in  the  figure  where  the  valve  is  shown  to  have  over- 
travel,  causing  the  width  at  F  to  be  less  than  that  of 
port  B.  If  the  valve  have  steam  lap  and  no  overtravel, 


20 


MODERN  STEAM  ENGINES. 


the  lap  permits  a  freer  exhaust,  as  shown  in  Fig.  17 
where  the  valve  has  steam  lap  equal  to  the  width  of  the 


port,  and  is  shown  in  the  position  it  would  occupy  when 
the  piston  was  at  the  end  of  a  stroke,  and  ready  to 
make  the  next  in  the  direction  of  arrow  G.  The  ex- 
haust port  B  is  here  fully  open,  and  this  shows  us  that, 


Fig.    17. 

unless  exhaust  lap  is  employed,  steam  lap  permits  the 
steam  to  exhaust  earlier  than  it  otherwise  would  do. 
This  is  shown  in  Fig.  18,  in  which  the  valve  has  lap 
equal  to  half  the  width  of  the  steam  port,  it  being  obvi- 


Fig,  18. 


ous  that  the  valve  edge  F  must,  in  any  case,  meet  the 
port  edge  b,  at  the  dotted  line,  by  the  time  the  piston 
has  arrived  at  the  end  of  the  stroke.  In  the  absence 


of  steam  lap,  the  exhaust  edge  c  of  the  valve  would  be 
coincident  with  edge  e  of  the  port  when  the  piston  was 
at  the  end  of  its  stroke;  hence  the  port  d  would  still  be 
closed,  whereas,  having  steam  lap  to  one-half  the  port 
width,  the  exhaust  is  open  to  one-half  that  width,  plus 
the  amount  of  lead  when  the  piston  is  at  the  end  of  its 
sti-oke.  Since,  however,  the  piston  is,  at  this  part  of  its 
movement,  traveling  very  slowly,  while  the  valve  move- 
ment is  at  about  its  quickest,  the  steam  is  not  exhausted 
much  too  early  in  the  stroke  unless  the  valve  has  a  max- 
imum of  steam  lap,  or  an  amount  more  than  equal  to 
the  steam  port  width ;  in  which  case  the  evil  may  be,  to 
some  extent,  remedied  by  giving  it  exhaust  lap. 

THE    IRREGULARITY    OF    THE    PISTON    MOTIOM. 

The  action  of  a  slide  valve,  having  an  equal  amount 
of  steam  lap  for  each  cylinder  steam  port,  is  not  the 
same  for  the  two  piston  strokes  occurring  during  a  com- 
plete revolution  of  the  crank. 

This  may  be  seen  from  Fig.  19,  in  which  the  piston 
is  shown  in  the  middle  of  the  cylinder,  and  the  crank 
at  mid  position,  or  half  way  between  its  points  of  dead 
center.  Suppose  now  that  we  take  the  distance  from  the 
center  A  of  the  crank  to  the  center  of  the  cross-head, 
and  we  may  mark  an  arc  F,  but  if  we  take  the  same 
distance  or  radius,  and  from  the  center  of  the  crank 
pin  mark  a  second  arc,  it  will  be  at  E,  showing  that 
the  piston  will,  with  the  crank  in  the  position  shown,  be 
pulled  forward  to  the  amount  of  the  distance  between  E 
and  F  on  the  line  of  centers  of  the  engine  (as  the  line 
passing  through  the  center  of  the  cylinder  bore  to  the 
center  of  the  crank  shaft  is  called).  This  is  due  to  the 
connecting  rod  which,  during  that  part  of  the  piston 
stroke  in  which  it  moves  away  from  the  line  of  centers, 
retards  the  motion  of  the  piston,  while,  during  that  part 
of  its  motion  in  which  its  crank  end  is  approaching  the 
line  of  centers,  it  causes  the  piston  motion  to  accelerate. 

At  all  times,  except  when  the  crank  is  on  a  dead 
center,  or  dead  point,  the  connecting  rod  is  at  an  angle 
to  the  line  of  centers  D,  D,  and  the  variation  of  piston 
speed,  above  referred  to,  is  said  to  be  due  to  the  angu- 
larity of  the  connecting  rod,  meaning  its  angle  to  the 
line  of  centers  of  the  engine.  The  angularity  of  the 
eccentric  rod  or,  in  other  words,  its  movement  out  of  a 
straight  line,  also  causes  the  admission,  point  of  cut-off 


Tin:  ii;i:i-:<;L'J.MUTY  OF  Tin:  J-IHTON  MOTION. 


21 


and  release  of  the  steam  to  vary  for  the  two  piston 
kes.  hut  in  ;i  minute  decree  only;  unless,  indeed,  the 

eci-eiitric  nxl   is  unusually  short  in    proportion   to    the 

unt  of  valve  travel.     As  the  the   same   for 

the  connect  ing  rod   and  the  eccentric  rod   we  may 


stroke,  and  the  point  I  will  recede  from  the  crank 
center,  a  distance  equal  to  that  from  A  to  the  crank 
center  in  one  case,  and  to  that  from  C  to  the  crunk 
center  in  the  other  case.  Clearly,  then,  while  the  piston 
is  making  the  first  half  of  its  stroke,  the  crank  pin  will 


/•':/.   19. 


further  explain  it  in  connection  with  the  connecting  rod 

only. 

Thus  suppose  that  in    Fig.  20,  I  represents   the  center 
of  tin'  cross-head   journal    when    the    piston  is  at  half 


I 
0— 


j> 


Fig.  20. 


stroke  and  J  the  length  of  the  connecting  rod,  and  that 
the  dotted  line  B  represents  the  crank  throw  line  when 
at  half  stroke.  Let  the  dotted  circle  represent  the  path 
of  the  center  of  the  crank  pin  and  1,  2,  3,  4,  respective 
(|unrter-revolutions  of  the  crank  pin  center.  If,  then,  a 
pair  of  compasses  be  set  from  point  I  to  the  center  of 
the  crank  shaft,  and,  from  I  as. a  center,  an  arc  of  a 
circle  be  struck  it  will  be  denoted  by  K,  and  the  inter- 
section of  K  with  the  dotted  circle  will  be  the  location 
of  the  crank  pin  center  when  the  piston  is  at  half 
stroke.  This  is  obvious  because  when  the  crank  pin 
center  is  at  A,  the  piston  will  be  at  one  end,  and  when 
it  is  at  C,  the  piston  will  be  at  the  other  end  of  its 


move  from  its  dead  center  at  A  to  the  point  where  the 
arc  K  cuts  the  dotted  circle.  While  the  piston  is  mak- 
ing its  second  half  stroke,  the  crank  pin  center  will 
require  to  move  from  K  to  C,  and  as  the  length  of  the 
eccentric  rod  is  greater  in  proportion  to  the  valve  travel 
than  the  length  of  the  connecting  rod  is  to  the  piston 
stroke,  therefore  it  moves  at  a  more  uniform  speed  than 
the  piston  does,  and  the  points  of  cut-off,  release,  etc., 
of  the  steam  is  not  timed  equally  for  the  two  piston 
strokes. 

The  nature  of  the  variation  (considered  with  relation 
to  a  single  piston  stroke)  will  always  be  that  the  piston, 
starting  from  its  farthest  point  from  the  crank,  will 
travel  more  than  half  the  length  of  its  stroke  while 
the  crank  makes  its  first  quarter-revolution,  and  less 
than  half  its  stroke  while  the  crank  makes  its  second 
quarter.  But  considered  with  relation  to  a  full  revolu- 
tion of  the  crank,  the  piston  will  travel  the  least 
while  the  crank  is  making  the  half-revolution  furthest 
from  the  piston,  as  from  B,  past  C,  to  D. 

Referring  now  to  the  motion  imparted  by  the  eccen- 
tric to  its  rod,  and  comparing  it  with  that  of  the  crank 
and  piston  movements,  let  A,  B,  C,  D,  in  Fig.  21,  repre- 
sent the  four  quarters  of  the  crank  revolution,  and  E, 
F,  G,  H,  the  corresponding  eccentric  movements,  the 
dead  center  A  being  that  farthest  from  the  cylinder, 
and  it  will  be  observed  that  while  either  the  crank  or 
the  eccentric  is  moving  from  A  to  B,  the  linear  motion 
produced  by  the  rod  will  be  retarded  by  the  angularity 
of  the  rod  to  the  line  of  linear  motion,  while  when 


22 


MODI-: I! X  .S7Y-.MJ/   ENGINES. 


either  of  them  is  moving  from  B  to  C  the  angularity  of 
the  rod  will  cause  its  linear  motion  to  be  acceler- 
ated. From  C  to  D  the  linear  motion  would  also  be 
accelerated,  and  from  D  to  A  retarded. 


Fig.    21. 

Considered,  however,  with  relation  to  the  half-revolu- 
tion from  B,  past  C,  to  D,  the  rod  angularity  would  accel- 
erate, while  from  D,  past  A,  to  B  it  would  retard  the 
linear  motion  of  the  rod,  or,  what  is  the  same  thing,  of 
the  piston  or  valve,  as  the  case  may  be. 

But  when  the  eccentric  rod  connects  direct  to  the 
valve  spindle,  its  throw  line  will  always  be  somewhere 
between  B  and  C  when  the  crank  is  at  A,  its  exact  loca- 
tion depending  upon  the  amount  of  steam  lap  and  the 
lead  of  the  valve.  It  will  be  seen,  therefore,  that  there 
is  no  uniformity  between  the  variation  of  linear  motion 
given  to  the  piston  and  valve  by  their  respective  rods. 

The  amount  of  angular  advance  (which  in  the  shop  is 
sometimes  termed  eccentric  lead  or  lead  of  eccentric) 
necessary  to  give  to  a  valve  a  certain  amount  of  lead 
varies  with  the  throw  of  the  eccentric.  Suppose,  for 
example,  that  a  valve  has  no  steam  lap  and  that  it  be  re- 
quired to  have  say  -J  inch  lead,  then  the  amount  of  an- 
gular advance  of  eccentric,  necessary  to  give  this  ^  inch 
lead,  will  be  less  in  proportion  as  the  throw  of  the  eccen- 
tric is  greater.  To  demonstrate  this  let  A,  Fig.  22, 
represent  an  eccentric  whose  throw  line  may  be  moved 
from  C  to  D,  the  inner  circle  representing  the  path  of 
motion  of  the  eccentric  center  when  the  throw  line  is 
at  C  and  has  no  angular  advance,  while  the  dotted  circle 
is  the  path  of  motion  of  the  center  when  the  throw  line 
is  at  D  and  has  an  angular  advance  of  30°,  and  it  is 


clear  that  moving  the  throw  line  from  C  to  D  would  in- 
crease the  lead  more  if  the  path  of  the  center  of  the 
eccentric  was  on  the  dotted  arc  than  if  it  were  on  the 
inner  circle. 


— 30- 


Fig    22. 


Again,  the  angular  advance  of  an  eccentric  necessary, 
under  any  given  amount  of  valve  steam  lap,  to  produce 
a  given  amount  of  lead  will  vary  according  to  the  posi- 
tion of  eccentric  with  relation  to  the  crank,  and  this 
varies  with  the  construction  of  the  engine. 

It  has  been  shown,  in  Fig.  12,  that  when  the  valve 
connects  direct  to  the  eccentric  strap  the  throw  line  of 
the  eccentric  leads  the  crank.  But  when  a  rock  shaft 
is  employed,  the  throw  line  of  the  eccentric  follows  the 
crank,  thus  Fig.  23  represents  an  eccentric,  rock  shaft, 
and  valve  connection;  C  represents  the  crank,  and  I) 
the  eccentric  throw  line,  E  the  eccentric  rod,  R  the  rock 
shaft,  and  S  the  valve  spindle,  the  direction  of  crank 
movement  being  shown  by  the  arrow.  If  the  eccentric 
rod  is  attached  direct  to  the  valve  spindle,  without  the 
intervention  of  a  rock  shaft,  the  eccentric  throw  lino 
would  require  to  stand  at  F,  in  which  case  with  the 
same  lap,  lead,  and  travel  of  valve,  the  angular  advance 
of  the  eccentric  would  be  different,  on  account  of  the 
angularity  of  the  eccentric  rod.  To  demonstrate  this, 
Fig.  24  represents  two  eccentrics,  A  and  B;  P  repre- 
sents the  crank  pin  to  move  in  the  direction  of  the 
arrow;  C  represents  a  line  at  a  right  angle  to  the  crank 
throw  line,  and  D  the  throw  lines  of  the  two  eccentrics, 
both  standing  at  30°  angle  from  C.  The  circle  N  rep- 
resents the  path  of  the  center  of  the  eccentric,  hence 
its  diameter  equals  the  travel  of  the  valve.  Now  let 
the  line  E  represent  the  center  of  the  cylinder  ports 
(that  is  the  center  of  the  cylinder  exhaust  port),  and 
the  diameter  of  half  circle  F  (equal  to  the  diameter  of 
the  circle  N)  will  represent  the  travel  of  the  valve.  Let 


Dlill-:(JTLY  -\.\'D  L\'L>J/;/-:cT!.Y 


VALVE  MOTIONS. 


23 


G  and  II  represent  the  respect  ive  eccentric  rods  of  ennui 
length,  and  attached  direct  to  the  valve.  Then  in  mov- 
ing eccentric  A.  so  that  its  throw  line  moves  fnmi  ('  to 
i).  the  valve  will  move  from  E  to  I,  while  in  moving 


the  same  eccentric.  1!  being  the  i>osition  when  the  frank 
pin  is  on  tlie  dead  center  shown,  and  A  the  position 
when  tin; crank  is  on  the  other  dead  center. 

Then  let  E  represent  the  center  of  the  cylinder  ports, 


the  throw  lino  of  R  from  C  to  T>,  the  valve  moves  from 
E  lo  .}.  which  being  a  greater  distance  than  from  E  to  I, 
shows  that,  though  the  two  eccentrics  have  been  moved 
an  equal  amount,  the  valve  has  nut  moved  an  equal 
amount.  Suppose  that  the  extreme  diameter  of  the  half 
le  F.  or  the  two  lines  L,  II,  represent  the  steam 
edges  of  the  steam  ports,  then  there  will  lie  less  lead  at 
.1  than  at  1.  To  make  the  lead  equal,  the  angular  ad- 
vance of  eccentric  A  would  require  to  be  diminished. 


and  the  amount  of  lead,  given  by  the  two  eccentrics, 
varies  as  the  difference  in  distance  of  I  and  J  from  the 
diameter  of  F,  as  before.  To  equalize  the  lead,  the 
rod  G  may  be  shortened,  bnt  this  being  done,  the  travel 
of  the  valve  would  not  be  equal  on  each  side  of  the 
cylinder  ports. 

The  cause  of  this  variation  of  lead  (due  to  a  given 
and  equal  degree  of  angular  advance  of  eccentric)  be- 
tween a  directly  connected  valve  gear  and  one  having  a 


Now  A  occupies  the   position  necessary  when  a  rock 

shaft  is  used  (the  crank  leading  the  eccentric)  and  B  the 

;i  when    the  eccentric  is  attached   direct,   hence 

when  a  rock  shaft  is  used  less  angular  advance  of  eccen- 

necessary  to  give  a  certain  amount  of  lead,  though 

the  lap  and  travel  of  the  valve  remain  the  same. 

But  we  may  assume  A  and  B  to  be  two  positions  of 


24. 


rock  shaft,  or  is   indirectly  connected,  may  be  further 
explained  as  follows: 

In  Fig.  25,  let  c  and  c'  represent  the  throw  lines  of 
the  eccentrics,  while  the  yalve  ends  of  the  rods  are  at 
E,  then  in  moving  the  throw  lines,  or  the  centers  of  the 
eccentrics,  from  c  to  d  and  from  c'  to  d',  the  valve  end 
of  the  rod  H  moves  from  E  to  J,  and  the  valve  end  of 


24 


MODERN  STEAM  ENGINES. 


rod  G  from  E  to  I.  Let  the  linos  d  e  and  d'  e'  be  per- 
pendicular to  the  line  c  c'  and  parallel  to  the  line  K, 
and,  of  course,  they  are  equal,  e-ach  being  the  sine  of 
30°.  Now  let  the  eccentric  centers,  instead  of  moving 


/•'/,/.   25. 

along  the  circumference  of  the  circle,  move  the  one 
from  c  to  e,  the  other  from  c'  to  e',  then  the  valve  ends 
of  both  rods  will  be  at  the  point  S,  which  is  farther 
from  the  crank  shaft  than  E.  Then  while  one  eccen- 
tric center  moves  from  e  to  d  the  valve  end  of  rod  II 
moves  from  S  to  J,  which  equals  the  distance  c  to  d, 
since  e  d  is  parallel  to  the  line  K,  and  the  other  eccen- 
tric center  moving  from  e'  to  d'  moved  the  valve  end  of 
rod  G  from  S  to  /  =  the  distance  e'  to  d',  which  equals 
distance  e  to  d,  therefore  S  t  =  S  J,  and  E  i,  being  less 
than  S  *',  is  less  than  E  J. 

DIAGRAMS    OF    STEAM    DISTRIBUTION. 

The  manner  in  which  a  slide  valve  opens  the  ports 
for  the  admission  and  exhaust  of  the  steam,  and  the 
general  effect  produced  by  various  amounts  of  lap 
travel,  etc.,  may  be  very  clearly  perceived  from  the 
following  diagrams,  more  clearly,  it  is  believed,  than  by 
any  other  form  of  diagram.  In  our  first  example  sup- 
pose the  proportions  are  as  follows: 

Length  of  piston  stroke  24  inches. 

Length  of  connecting  rod  —         -     72 

"Width  of  steam  port  1 

"        "     bridge    -  3 
"        "     cylinder  exhaust  port         —       1 

Steam  lap  of  valve      —  0 

Exhaust  lap  of  valve  -$ 

Lead  of  valve  T' 

Width  of  valve  cavity       -  -      2^ 

Travel  of  valve  2 

The  construction  of  the  diagram  is  as  follows:  The 
line  A  B,  Fig.  26,  represents  the  full  stroke  of  the 
piston.  Line  C  C  is  drawn  parallel  to  A  B,  and  is  dis- 


tant  from  it  to  an  amount  equal  to  the  full  width  of  the 
cylinder  steam  port.  Line  D  D  is  also  parallel  to  A  B, 
and  distant  from  it  to  an  amount  equal  to  the  full  width 
of  the  cylinder  steam  port.  Line  A  B  is  divided  by 


1    2   3  t 

5678       10     12      14      16      18     20     22     24 

f 

'/ 

'/ 

- 

1 

r 

• 

^ 

•« 
, 

I 

i 

^ 

\ 

\ 

- 

j. 

" 

! 

5» 

i 

^ 

^ 

4       22     20      18      16      14     12      10      B   7   6  5  4  3    2 
/•)>/      'Ml 

the  vertical  lines  into  as  many  equal  divisions  as  there 
are  inches  in  the  piston  stroke — in  this  case,  24  inches. 
The  curved  line  on  the  upper  half,  that  is  between  A  B 
and  C  C,  shows  the  port  opening  to  admit  steam 
through  one  cylinder  port  and  the  lower  curved  line 
shows  the  exhaust  opening  of  this  same  port. 

The  dotted  curve  above  A  B  shows  the  port  opening 
for  the  admission  of  steam  for  the  other  cylinder  steam 
port,  and  the  dotted  curve  below  A  B  shows  the  port 
opening  during  the  exhaust  of  this  second  piston  stroke. 
The  manner  of  obtaining  these  curved  lines  was  as 
follows :  The  engine  fly  wheel  was  moved  around 
until  the  piston  had  moved  an  inch,  the  amount  the 
port  was  open  was  measured,  and  this  measurement  was 
marked  on  line  1  above  A  B.  The  piston  was  then 
moved  another  inch,  and  the  port  opening  again  meas- 
ured and  marked  on  the  second  vertical  line  above  A  B, 
and  so  on  throughout  every  inch  of  piston  movement 
for  that  stroke.  Thus  at  line  7,  the  piston  had  moved 
7  inches  from  its  dead  center  A  and  had  left  the  steam 
port  open  £  of  an  inch,  as  is  marked  in  the  diagram; 
or,  again,  when  the  piston  had  moved  21  inches,  the 
port  was  open  J  inch  as  marked  on  the  diagram. 
Through  the  points  thus  marked  on  the  vertical  lines  the 
full  curve,  starting  from  A,  passing  up  to  C  and  ending 
at  B,  was  marked,  thus  showing  the  port  opening  for 
every  inch  of  piston  movement  and  for  the  whole 
stroke.  For  the  exhaust  of  this  steam,  the  piston  was 
moved  an  inch  on  its  return  stroke  and  the  width  of 


DlA<:it.\MX  OF  VALVE  MOTIONS. 


the  same  port,  acting  as  an  exhaust  port,  was  meas- 
ured and  marked  fruiii  the  vertical  line  1  and  In-low  A 
I'.;  tin-  piston  was  then  moved  another  inch  and  tho  ex- 
haust opening  again  measured,  and  so  on  throughout 
the  whole  stroke;  thus  when  the  piston  had  moved  I 
inches  oil  its  return  stroke  the  exhaust  port  had  opened 
j  of  an  inch  as  marked  on  the  diagram. 

The  admission  and  exhaust  of  the  steam  for  the  other 
steam  port  was  obtained  and   marked  on  the  diagram  in 
the  same  way,  but  was  marked  in  the  dotted  cur\< 
as  to  distinguish  it. 

In  these  diagrams,  therefore,  the  actual  working  of 
the  valves  is  shown.  ?'rom  the  diagram  in  Fig.  'J<>  we 
jK'iveivr  that  the  steam  ports  were  not  opened  full  until 
the  piston  had  moved  \'l  inches  on  one  stroke,  and  11 
inches  on  the  other  stroke,  and  that  the  exhaust  port 
was  not  opened  full  until  the  piston  had  moved  '.<  inches 
on  one  stroke,  and  did  not  open  quite  full  for  the  other 
Ice. 

In  the  full  linn  diauram,  the  port  opened  slower  and 
wer  for  the'  live  steam,  but  opened  quicker  and 
•licker  for  the  exhaust  steam.  There  was  no 
expansion  (that  is  to  say,  the  steam  followed  full  stroke) 
and  no  cushion,  the  steam  exhausting  during  the  entire 
stroke.  To  show  the  effect  of  steam  lap,  let  £  inch  of 
:n  lap  lie  added  to  this  valvo  which  will  necessitate 
making  the  cylinder  exhaust  port  2  inches  wide  instead 
of  1  as  before,  widening  the  valve  exhaust  port  from 
inches  to  3-^  inches  and  increasing  the  valve 
travel  from  '2  to  :;\  inches.  In  both  cases,  the  travel 
of  the  valve  is  equal  to  twice  the  width  of  the  steam 
port  added  to  twice  the  amount  of  the  steam  lap,  and 
the  valve  exhaust  port  has  -Js  of  an  inch  exhaust  lap, 
while  the  cylinder  exhaust  port  is  equal  in  width  to 
twice  the  width  of  the  steam  port,  added  to  the  amount 
of  steam  lap  on  the  valve,  these  proportions  being  those 
which  (disregarding  the  slight  error  or  variation  due  to 
the  angularity  of  the  eccentric  rod)  just  gives  a  valve 
travel  sufficient  to  open  the  ports  fully  as  steam  and  ex- 
haust ports. 

A  diagram  of  the  valve  movement,  under  this  new 
condition,  is  shown  in  Fig.  27,  and  we  find  the  effect  of 
adding  the  steam  lap  to  be  a  much  quicker  port  open- 
ing to  admit  steam  and,  in  the  full  line  diagram,  a  clos 
ure  of  the  valve  at  19£  inches  of  piston  movement,  the 


steam  being  shut  in  by  the  valve  and  working  expan- 
sively durin.ir  the  next  .">  inches  of  piston  movement, 
the  exhaust  opened  when  the  piston  had  traveled  about 
'J2|  inches  and,  therefore,  1J  inches  before  the  piston 
had  arrived  at  the  end  of  its  stroke.  The  exhaust  was 


4 

- 

I     10    1 

Z      14     1 

5     18     20     22     24 

/ 

' 

' 

'    . 

> 

> 

s 

. 

•• 

, 

' 

\ 

\ 
\ 

S 

\ 

^ 

"  . 

\\ 

' 

s 

\ 

\ 

N 

V 

•  , 

16     H     12      10      B  7  6  5  4   3   2    I 


Fig.  27. 

full  open  when  the  piston  had  moved  f  inch  on  its 
return  stroke,  remaining  full  open  while  the  piston 
moved  to  its  16th  inch  of  movement,  and  finally  closing 
at  the  22nd  inch  of  piston  movement,  when  it  shut  in 
the  steam,  giving  '1  inches  of  cushion  or  compression. 

Comparing  one  stroke  with  the  other,  there  is  2^ 
inches  difference  in  the  amount  of  the  expansion,  $•  inch 
in  the  commencement  of  the  exhaust,  or  point  of  re- 
lease, and  £  inch  difference  in  the  amount  of  compres- 
sion. 

These  variations  are  due  to  the  angularity  of  the 
connecting  rod  which  has  been  already  explained.  But 
in  the  full  line  diagram  the  port  has  not  opened  fully, 
and  this  is  due  to  the  angularity  of  the  eccentric  rod. 

We  may  now  examine  some  of  the  means  that  may 
be  employed  to  equalize  these  differences  and  to  detain 
the  steam  longer  in  the  cylinder.  First,  to  prolong  the 
point  of  release,  let  us  take  the  same  valve,  under  pre- 
cisely the  same  conditions  as  for  the  last  diagram,  and 
give  to  it  -^  of  an  inch  of  exhaust  lap,  and  the  dia- 
gram of  the  port  openings  is  given  in  Fig.  28. 

Here  we  have,  as  a  marked  and  entirely  new  feature, 
the  circumstance  that  the  exhaust  port  opens  full  and 
immediately  begins  to  reclose,  which  is  caused  by  the 
exhaust  lap  partly  closing  the  cylinder  exhaust  port  as 
shown  in  Fig.  29,  at  A,  where  the  width  is  less  than 
it  is  at  B. 


26 


MODERN  STEAM  ENGINES. 


It  is  laid  down  by  most  of  those  who  have  investi- 
gated the  subject  that  the  port  should  permit  about  one- 
half  more  opening  for  the  exhaust  than  for  the  live 


5  3  4    5  6  7   8       10 


\ 


\ 


12 


14     115     18     20      22     24 


24      22    ZO       IS      16    '14     12       10 

Fig,  28. 


8   76543:! 


steam,  because  of  the  diminishing  pressure  and  velocity 
of  the  steam  in  leaving  the  cylinder.  Now  if  we  add 
up  the  length  of  all  the  vertical  lines,  measured  from 
the  line  A  B,  in  Fig.  27,  to  the  line  of  the  upper  curve, 
and  divide  by  the  number  of  vertical  lines  so  meas- 


Fig.  29. 

ured,  we  shall  obtain  the  average  port  opening  for  the 
live  steam,  and,  by  a  similar  process,  the  average  ex- 
haust opening  may  be  obtained,  but  a  glance  will  show 
that  in  Fig.  28  there  is  but  little  if  any  difference, 
while  actual  measurement  will  show  them  practically 
equal.  The  exhaust  could  not,  in  this  case,  be  free  dur- 
ing the  early  part  of  the  stroke,  hence  a  back  pressure 
would  be  induced  which  would  more  than  off-set  the 
advantage  gained  by  the  prolongation  of  the  points  of 
release  which  is  shown  by  the  diagrams  to  have  taken 
place.  It  will  be  observed,  however,  that  the  addition 
of  the  exhaust  lap  has  increased  the  cushion,  or  com- 
pression, from  about  2  inches,  in  Fig.  27,  to  3  inches 
in  Fig.  28. 

It  is  here  to  be  observed  that  the  defect,  shown  in 


the  exhaust,  may  be  remedied  by  increasing  the 
width  of  the  cylinder  exhaust  port,  which  would  also 
involve  a  corresponding  increase  in  width  of  the  valve 
exhaust  port.  Or  the  width  of  the  bridges  between  the 
cylinder  ports  and  the  valve  exhaust  port  might  be 
widened,  which  would  accomplish  the  same  result. 

The  points  of  full  port  opening,  port  closure,  point  of 
release,  and  point  of  compression  may  be  made  more 
uniform  for  the  two  piston  strokes,  by  giving  to  a  valve 
an  increase  of  travel,  thus,  in  Fig.  30,  is  represented  a 


\ 


\ 


\ 


Fig.  30. 

diagram  of  the  port  openings  of  a  valve  motion  navmg 
the  following  elements  : 

"Width    of  Steam  ports  1^  inches 

"         "   Bridges  -        1 

"         "    Cylinder  exhaust  port  -            1\ 

"         "   Steam  lap  f 

"         "    Exhaust  lap  ^ 

Travel  of  valve         -  -        5| 

These  dimensions  represent  the  average  employed 
upon  American  passenger  locomotives  having  pistons 
16  inches  diameter  and  24  inches  stroke,  the  port  open- 
ings and  closures  are  here  seen  to  be  very  nearly  equal 
for  both  strokes,  but  the  average  exhaust  area  is  lees 
than  the  average  steam  area,  on  account  of  the  valve 
traveling  so  far  as  to  partially  close  the  cylinder  ex- 
haust port,  as  shown  in  Fig.  31  at  F,  where  the  opening 
is  less  than  at  B. 


llo/.AV.Y'/  N77-.M.1/   EXPANSIVEL  Y. 


27 


The  exhaust,  however,  will  i  mped  providing 

;i  of   the   cylinder  exhaust    poll    is  equal 

area  of  the   nox/.le  of  the  exhaust    p i|>e.    which. 

in  American   practice,  is   limited  so  as  to   pro, luce  sufli- 

cicnt    draft     for   the  combustion  of   the   fuel  ill   the   lire- 


Fift.  .".'_'  represents  a  diagram  of  the  port   oj>eni 
a  valve  motion,   having   precisely   the   same   dimensions 
except  that  there  i-  ^  inch  more  steam  lap,  and  the  valve 
j   inches  only,   instead  of  5|,    the   4i  inches 
I  inch   more  than  twice  the  width  of  steam  port, 
plus  twice  the  steam  lap. 


\ 


\ 


\ 


\? 


\\ 

N 


\\ 


Fi'j.  32. 

The  main  point  of  difference  between  these  last  two 
diagrams  is  that  in  the  first,  the  average  steam  opening 
is  1.07  inches,  average,  width  of  exhaust  opening  ^ 

of  an  inch.     In  the  last,  there  is  an  average  steam  port 
4 


opening  '  ID  inch,  and  an  average  exhaust  open- 

1  1>l|=i   inches. 

>.M     KAI'ANSIOX. 

A  slide  valve  of  the  form  hitherto  referred  to  will 
not  serve  tn  advantage  to  cut  off  the  steam  at  a  period 
earlier  than  at  about  three-<|iiarters  of  the  stroke,  leav- 
ing the  remaining  quarter  stroke  to  be  made  under  ex- 
pansive steam,  became  when  the  amount  of  steam  lap 
is  excessive,  the  exhaust,  occurs  too  early,  and  further- 
more the  admission  and  amount  of  expansion  varies 
gl-eath  in  one  stroke  as  compared  to  (he  oilier. 

The  object  of  using  tin'  steam  expansively  is  to 
obtain  more  duty  from  it  before  it  is  exhausted  into  the 
atmosphere:  suppose,  for  example,  that  the  stroke  of 
a  piston  is  l'_'  inches,  and  that  after  it  has  traveled  6  of 
these,  the  supply  of  steam  to  the  piston  is  cutoff  by 
the  valve,  then  all  the  work  done  by  the  steam,  during 
the  remaining  H  inches  of  piston  stroke,  is  obtained 
without  taking  any  more  steam  from  the  steam  chest, 
or  what  is  the  same  thing,  from  the  boiler.  The  abso- 
lute jiower  of  a  given  cylinder  is,  of  course,  diminished 
in  proportion  as  the  steam  is  worked  expansively,  be 
cause  the  steam  pressure  decreases  in  the  ratio  that  its 
volume  is  increased,  thus  suppose  we  have  a  cylindei 
10  inches  long,  and  that  6  inches  of  its  length  is  filled 
with  steam  at  a  pressure  of,  say,  50  Ibs.  per  square  inch 
of  piston  area,  and  that,  no  more  steam  being  admitted, 
the  piston  moves  down  the  cylinder,  then  the  steam 
pressure  would  diminish  as  the  piston  moved,  the  pres- 
sures at  the  end  of  each  inch  of  piston  motion  being  as 
marked  in  Fig.  33.  When  the  piston  had  moved  from 
the  sixth  to  the  seventh  inch,  the  steam  would  occupy 
one-seventh  more  space,  hence  its  pressure  would  be 
one-seventh  less,  therefore  we  reduce  the  50  one-seventh, 
obtaining  42.86  as  the  pressure  at  the  end  of  the  seventh 
inch  of  piston  motion.  When  the  piston  had  moved 
from  the  seventh  to  the  end  of  the  eighth  inch  of  its 
stroke,  the  steam  would  occupy  one-eighth  more  space 
than  it  did  at  the  end  of  the  seventh,  or  what  is  the 
same  thing,  than  it  did  at  the  beginning  of  the  eighth 
inch  of  its  motion;  hence  the  pressure  of  42.8(3  Ibs. 
would  be  reduced  one-eighth,  making  it  37.51  Ibs.  at 
the  end  of  the  eighth  inch  of  the  piston  stroke,  and  so 
on  throughout  the  whole  stroke.  To  obtain  the  average 
pressure  of  the  steam  throughout  the  whole  stroke,  we 


28 


MODERN  STEAM  ENGINES. 


add  together  the  pressure  at   the  end  of  each  inch  of 
piston  stroke  and  divide  the  sum  so   obtained  by  the 


PKfSSURC 
5016s. 


50  ' 


50" 


50' 


50" 


42' 86 


37 '51 " 


Fig.  33. 

number  of  inches  in  the  whole  stroke  which  gives  the 
average  pressure.     Thus 


Pressure  at  end  of 


LBS.  PER 

SQ.   IX. 

1st  in.  of  piston  motion  50 


it 
a 


2nd 
3rd 
4th 
5th 
6th 
7th 
8th 
9th 
10th 


50 

50 

50 

50 

50 

42.86 

37.51 

33.34 

30.01 


443.72 

and  443.72  divided  by  10  equals  44.37,  hence  the  aver. 
age  pressure  is  44.37  Ibs.  per  square  inch  of  area. 

THE    ALLEN    VALVE. 

If  sufficient  steam  lap  be  given  to  a  common  D  valve, 
(such  as  has  thus  far  been  considered)  to  enable  it  to 
cut  off  the  steam  earlier  than  at  about  five-eighths  of 
the  stroke,  the  throw  of  the  eccentric  requires  to  be  so 
much  increased,  in  order  to  obtain  sufficient  valve 
travel,  that  the  angularity  of  the  eccentric  rod  causes 
the  points  of  cut-off  to  vary  to  an  objectionable  degree  ; 
this  may  be  remedied  by  giving  to  the  valve  a  different 


amount  of  steam  lap  for  each  steam  port.  There  are, 
however,  objections  to  this  which  will  be  explained 
hereafter. 

An  early  point  of  cut-off,  with  a  minimum  of  travel 
and  a  maximum  amount  of  port  opening  may,  however, 
be  obtained  by  the  use  of  Allen's  valve,  which  we  may 
now  consider  with  relation  to  cutting  off  at  some  defi- 
nite point,  leaving  its  employment  in  connection  with 
the  link  motion  to  be  treated  of  in  connection  with  that 
subject.  The  construction  of  the  Allen  valve  is  shown 
in  Fig.  34,  in  which  the  valve  is  shown  in  mid  position. 


Fig.   34. 

A  A  is  a  supplementary  steam  port,  which  acts  to  admit 

steam  as    well    as    the    steam    edge    g    of    the    valve. 

Fig.  35  shows  the    valve  in  its   position    when    the 


Fig.  35. 

crank  is  on  the  dead  center,  and  it  is  seen  that  when  the 
valve  moves  to  the  right,  steam  will  be  admitted  to 
port  K  by  the  edge  g  and,  simultaneously,  through  the 
supplementary  port  as  denoted  by  h. 

In  Fig.  36,  the  valve  is  shown  at  the  end  of  its  travel, 
the  port  K  being  closed  to  the  amount  of  the  thickness 


APPLICATION   '>!•'  Till-:  ALLEN    VALVE  To  I-'IXEU  POIXTs  OF  CUT-OFF. 


29 


of  metal  at  c,  a  c  ace  that  ia  taken  into  eonnder- 

i  in  determining  tin-  wiilth  of  the  steam  port. 

The  exhaust  is  effected  in  tlie  same  manner  as  in  a 
simple  sliile  valve,  ami  independently  of  the  supple- 
mental port,  as  may  he  seen  frmii  the  ligure. 

The  steam   lap  of  the  valve  is  the   distance   from    the 
inner  edge  (/'.    Fig.  :!7)of  the  supplementary  port 
outer  edge  -/.  this  being  the   amount  the   valve  overlaps 


/'/,/.  36. 

•  •am   port  when  in  its  mid  position,  as  shown  in 
Pig.  34. 

The  steps  n.  Fig.  37,  in  the  valve  seat,  must  be  fair 

with  the  edge  d  of  the  supplementary  port,   when  the 

/  is  fair  with  the  outer  edge,  or  steam  edge,  of 

port   K.  so  that  when  the  valve  moves  to  open  port  K 

"urn  will  he  admitted  simultaneously  through  the 


F,g.   37. 

supplementary  port  and  through  the  port  opening  left 
by  the  edge  g,  as  the  valve  moves  in  the  direction  de- 
noted by  the  arrow  E. 


The  width  of  I!.  Fie;.  :'.!.  must  lie  sullieient  to  cover 
the  steam  port  and  keep  it  steam  tight  when  the  valve 
is  in  mid  position,  and  for  this  purpose  .,'.,  of  an  inch  on 
each  side  will  sullice,  making  H  ^  of  an  inch  wider 
than  the  steam  port. 

The  inner  edges  of  the-  supplemental  steam  port  must 
be  fa  of  an  inch  wider  than  the  extreme  width 
of  the  outer  edges  of  the  cylinder  steam  ports,  so 
as  to  isolate  the  ports  when  the  valve  is  in  mid  posi- 
tion. 

We  now  come  to  the  width  of  the  supplementary 
port,  and  it  is  obvious  that  the  thickness  at  <,  Fig.  MI;, 
must  lie  enough  to  leave  sufficient  strength,  and.  since 
this  thickness  covers  the  port,  as  seen  in  the  figure,  it  is 
desirable  to  leave  it  no  more  than  its  strength  requires, 
thus  leaving  the  supplementary  port  as  wide  as  pos- 
sible. 

By  the  employment  of  the  supplementary  port  the 
steam  port  is  opened  quicker,  remains  full  open  longer 
and  closes  quicker.  On  referring  again  to  Fig.  35, 
it  will  be  seen  that  if  the  valve  were  moved  •£  inch  the 
port  would  be  left  open  |  inch  at  g  and  ^  inch  at  //,  and 
when  the  valve  had  arrived  at  the  position  shown  in 
Fig.  38  the  port  will  be  opened  the  amount  at  g  and 


Fig.  38. 

the  full  width  of  the  supplementary  port,  as  seen  at  h,  e, 
whereas  a  common  slide  valve  would  have  the  opening 
at  g  only.  As  the  valve  motion  continues,  the  port 
opening  remains  full  because  to  whatever  amount  the 
supplementary  port  closes  at  e,  the  opening  at  g  in- 
creases. Similarly  after  the  valve  has  finished  its  stroke, 
and  is  returning  to  effect  the  cut-off,  the  full  port 
opening  will  be  maintained  until  the  valve  has  trav- 


f     ^        I  > 

MJNIVERSITYy 


30 


MODERN  .ST/-AU/   ENGINES. 


eled  back  to  the  position  shown  in  the  figure,  the  open- 
ing at // and  at,  -  being  equal.  Suppose,  for  example, 
the  valve  has  traveled  back  as  far  as  shown  in  Fig.  39, 


Fig.  39. 

and  to  whatever  amount  g  closes,  the  supplemental  port 
will  open,  thus  maintaining  the  full  port  opening.  This 
will  continue  until  the  openings  at  g  and  e  are  of  equal 
width,  after  which  time  the  end  d  of  the  supplementary 
port  will  close  as  rapidly  as  the  edge  g  does. 

We  have  here  considered  the  working  of  the  Allen 
valve  for  latb  points  of  cut-off  only,  and  its  action  may 
be  seen  by  referring  to  Fig.  40  and  41,  the  former 


\ 


\ 


\ 


/ 


\ 


\ 


X 


\ 


\ 


\ 


\ 


\ 


32  f 

Fig.  40. 

showing  the  port  openings  of  a  common  slide  valve, 
and  the  latter  of  the  Allen  valve.  Both  valves  have 
If-  inches  steam  lap  and  54.  inches  travel.  The  width  of 
port  for  the  common  valve  is  14,  and  that  for  the  Allen 


valve  If,  the  thickness  c,  Fig.  36,  being  §,  leaving  the 
effective  steam  port  opening  \\  inches  ;  as  an  exhaust 
port,  however,  there  is  a  full  opening  of  If  inches. 

/3    ft 


\ 


\ 


\ 


\ 


\ 


\ 


f\ 


/6 

Fig.  41. 
A   comparison  of  the  two  diagrams  gives  us  as  follows 

for  the  forward  stroke  : 

Allen  Common 

valve,  valve. 

Amount  of  piston  motion  before  the        IN.  ix. 

port  had  opened  full                                        \  4$ 
Inches  of  piston  motion  under  a  full 

port  opening                                       -        13  6^ 

Point  of  cut-off                                               1G|  15£ 

Point  of  release                                     -       21 J  21 

Cushion                                                            If  2-J 

It  is  seen,  therefore,  that  the  advantage  is  on  the 
side  of  the  Allen  valve  in  every  particular,  and  it  is  to 
be  noted  that  we  may  add  to  the  Allen  valve  sufficient 
exhaust  lap  to  prolong  the  point  of  release  to  22J 
inches,  and  thus  keep  the  steam  in  during  1^  inches 
more  of  piston  stroke  while  having  the  same  amount 
of  cushion  as  the  common  valve.  The  two  points  of 
cut-off  for  the  Allen  valve  are  at  16^  and  at  17£  inches 
respectively  of  piston  motion,  a  variation  of  one  inch 
only,  while  for  the  common  valve  we  have  the  point  of 
cut-off  at  15  inches  for  one  stroke  and  17^  for  the 


.i />/'/./r,i  VYO.Y  or  TIII-:  ALLEN  VALVE  TO  i-'i.\i-:i>  />o/.\rs  or  CUT-OFF. 


other,   a  variation  of   1J    inches.     The  point    of  release 
varies  in  I  the   Allen  valve  .1   inch  only,  while 

in  tin'  case  of  the  eoininon  valve  n   \anes  an  inch. 

If    we  give    tn    the  valve   sullicient    travel    to  rinse  the 
supplementary   port,  as  shown    in    Fig.  U.  \\v  may  give 


42. 


to  the  v:ilve  as  niucli  steam  lap  as  the  common  slide 
valve  ami  get  a  much  lietter  distribution  of  steam  as 
has  lieen  shown.  luit  we  may  give  to  die  valve  only 
siillicient  travel  to  cause  it.  at  the  end  of  its  stroke,  to 
come  to  the  position  .shown  in  Fig.  38,  the  opening  at 
.•,|iial  to  the  width  of  the  supplementary  port 
and  thus  enalile  the  valve  to  cut-off  at  early  points  in 
the  stroke  without  the  employment  of  excessive  steam 
lap  and  valve  travel,  while  obtaining  a  better  steain  sup- 


43. 


ply  than  with  the  common  valve,  and  avoiding  the 
irregularities  in  the  points  of  cut-off  of  release  and  of 
compression  that  arises  when  the  amount  of  steam  lap 
is  excessive,  as  \\  or  \\  times  the  width  of  the  steam 
port. 

Fig.   43  shows   the  valve  in  mid  position,   the   lap 


befog  ao  proportioned  to  the  port  width  that  when  the 

valve  is  at  the  end  of  iis  stroke,  as  in  Fig.  IIS.  the  open- 
ing at  i/  is  equal  to  the  width  of  the  supplementary  port. 
To  find  the  amount  of  lap  necessary  to  accomplish  this 
result  and  the  width  of  the  supplementary  port,  we  sub- 
tract the  thickness  of  metal  lictween  edge  g  and  the 
supplementary  port  from  the  width  of  the  steam  port, 
and  divide  the  remainder  by  two,  and  the  sum  so  ob- 
tained will  be  the  width  of  supplementary  port  neces- 
sary to  give  at  </  opening  equal  to  the  supplementary 
port.  By  adding  the  width  of  the  supplementary  port 
to  the  thickness  of  the  metal  at  g  we  obtain  the  amount 
of  steain  lap.  The  correctness  of  this  method  will  be 
seen  on  referring  again  to  Fig.  38,  where  it  is  plain  that 
the  openings  at  g  and  r  are  equal,  and  when  added  to  the 
thickness  of  g  equal  the  width  of  the  port.  If,  in  order 
to  effect  an  early  point  of  cut-off,  we  were  to  increase 
the  amount  of  steain  lap,  we  must  correspondingly  in- 
crease the  valve  travel,  and  the  opening  at  g  will  be 
diminished. 

In  Fig.  43  «,  we  have  a  diagram  of  the  port  openings 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


V 
A 


Fig.  43  a. 

of  an  Allen  valve,  the  steam  port  being  1£  inches,  but 
as  the  thickness  at  e,  Fig.  39,  is  f  inch,  the  effective 
port  width  is  1^  inches.  The  steam  lap  is,  therefore, 


32 


MODERN  STEAM  ENGINES. 


\\  inches  (width  of  port  If  less  thickness  at  e  f  =  1^) 
and  the  travel  is  4^  inches  (twice  the  width  of  the  port 
If  inches  added  to  the  amount  of  steam  lap,  l\  inches, 
=  4^).  Now  the  common  valve,  whose  port  open- 
ings were  shown  in  Fig.  40,  had  If  steam  lap  and  yet 
the  steam  followed  15^  inches  on  one  stroke  and  17^-  on 
the  other,  whereas  in  this  case  there  is  -J  inch  less  lap 
and  the  valve  cuts  off  at  11  inches  on  one  stroke  and 
11-J  on  the  other,  which  occurs  on  account  of  the  re- 
duced travel.  Furthermore,  the  admission  is  more  full 
and  the  cut-off  much  sharper,  evidencing  the  superior- 


ity of  the  Allen  valve  for  early  cut-offs.  The  exhaust 
is  opened  very  freely,  and  would  begin  at  19^  inches 
on  the  forward  stroke,  but  by  adding  ll-;1^  inches  of 
exhaust  lap,  the  point  of  release  is  at  the  22nd  inch  for 
one  stroke  and  at  22^  inches  for  the  other.  The  com- 
pression occurs  at  17£  inches  on  one  stroke  and  16 
inches  on  the  other,  which  is  not  objectionable  consid- 
ering the  early  part  of  cut-off,  and,  also,  that  the  port 
opens  to  its  full  width  of  If  inches  when  acting  as  an 
exhaust  port. 


CHAPTER    II. 


DIAGRAMS  FOR  DESIGNING   VAI.VE  MOTIONS  OR  MECIIASISMS. 


The  action  of  a  given  slide-valve  mechanism  may  be 
investigated,  or  ihr  proportions  of  hip.  lead,  travel,  etc., 
necessary  to  admit  cut-oil,  and  exhaust  the  steam  at 
predetermined  points  in  the  piston  strokes,  may  be  found 
liy  u  combination  of  lines  forming  a.  diagram,  the  prin- 
ciples involved  in  constructing  such  diagrams  bring  as 
•AS  :  The  path  of  motion  of  the  center  of  an  eccen- 
tric describes  a  circle,  whose  diameter  equals  the  travel 
the  eccentric  will  give  to  the  valve.  Thus,  in  Fig.  44, 


/•"/'/.   44. 

is  shown  an  eccentric  in  two  opposite  positions.  Its  shaft 
center  is  at  C.  When  the  eccentric  is  in  the  position 
marked  1,  its  center  is  at  T>,  and  its  throw  is  the  distance 
from  C  to  D.  If  the  shaft  revolves  the  eccentric  one- 
half-revolution,  the  point  D,  revolving  about  the  center 
C,  will  arrive  at  B,  and  the  eccentric  will  stand  in  posi- 
tion 2.  If  the  shaft  makes  another  half-revolution,  the 
point  D  will  again  reach  the  position  it  occupies  in  the 
tigiire,  its  whole  path  being  denoted  by  the  dotted  circle 
D  B. 

That  the  diameter  of  this  dotted  circle  is  equal  to  the 


whole  of  the  movement  the  eccentric  is  capable  of  mov- 
ing its  rod  in  a  straight  line,  may  be  shown  as  follows: 
Suppose  the  eccentric  is  in  position  2,  and  the  direc- 
tion of  rod  motion  is  on  the  line  A  B,  and  that  a  pencil 
point  be  rested  against  the  eccentric  at  x,  then  when  the 
eccentric  had  made  a  half-revolution  it  would  move  the 
pencil  along  the  dotted  line  from  x  to  y,  and  from  x  to 
y  is  the  same  distance  as  from  D  to  B.  Or  suppose  that 
— the  eccentric  being  in  position  1 — we  set  a  pair  of 
compasses  to  the  length  of  the  eccentric  rod  and,  rest- 
ing one  point  at  D,  we  may  mark  the  arc  passing 
through  the  dot  at  A.  Then  resting  one  point  at  B  we 
mark  dot  S,  and  from  A  to  S  is  the  amount  the  eccen- 
tric is  capable  of  moving  the  valve,  and  is  also  equal  to 
the  distance  from  D  to  B.  If  we  wish  to  find  how 
much  the  eccentric  has  moved  the  valve  while  moving 
from  one  point  to  another  in  its  path,  we  proceed  as  in 
Fig.  45,  in  which  B  represents  the  point  the  eccentric 


Fig.  45. 

started  from,  and  g  the  point  it  has  arrived  at,  and  to 
find  how  much  it  has  moved  its  rod  in  a  straight  line, 


33 


34 


MODERN  STEAM  ENG1M-:*. 


all  we  have  to  do  is  to  mark  a  line  /  at  a  right  angle  to 
the  line  A  B,  thus  producing  the  point/  on  line  A  B, 
and  from /to  B  is  the  distance  the  rod — or,  what  is  the 
same  thing,  the  valve — was  moved  on  the  line  A  I!, 
while  the  eccentric  center  moved  from  B  to  //. 

Tho  path  of  the  crank  pin  is  obviously  also  a  circle, 
whose  diameter  equals  the  stroke  of  the  piston,  and  may, 
therefore,  be  taken  to  represent  it,  and  if  we  leave  the 
length  of  the  connecting  rod  out  of  mind,  or  suppose  it 
to  be  so  great  as  not  to  cause  the  piston  motion  to  be  ac- 
celerated at  one  part  and  retarded  at  another  part  of  its 
stroke,  we  might  find  the  position  of  the  piston,  for  any 
position  of  crank  pin,  by  lines  in  the  same  way  as  we 
have  done  in  the  case  of  the  eccentric.  In  Fig.  46.,  for 


Fig.  46. 

example,  the  circle  represents  the  crank  pin  path,  and  i 
the  position  of  the  crank  pin,  the  piston  being  at  C. 
Similarly,  throughout  the  whole  figure,  one  end  of  each 
vertical  line  may  be  taken  to  represent  the  position  of 
the  piston,  and  the  other  end  of  the  same  line  will  rep- 
resent the  corresponding  position  of  the  crank  pin. 
Now,  as  both  the  valve  and  crank  pin  motions  may  be 
represented  on  a  circle,  it  will  be  obvious  that  we  might 
use  the  same  circle  to  represent  the  two,  using  separate 
dots  to  denote  their  relative  positions.  In  Fig.  47, 


the  valve  travel  is  1  inch,  and  the  circle  will  represent 
it  full  size,  so  that  every  -,1F  inch  on  the  diameter  will 
represent  -fa  inch  valve  travel.  Now,  suppose  that  the 


/•'///.   47. 

piston  stroke  is  16  inches,  and  the  circle,  being  but  1 
inch,  is  fa  full  size  when  considered  to  represent  the 
crank  pin  path,  and,  being  fa  full  size,  every  division 
on  its  diameter  will  represent  an  inch  of  piston  move- 
ment ;  hence  in  using  the  same  circle  for  both  crank 
pin  and  eccentric  path,  all  we  require  to  consider  is  that 
its  diameter  represents  both  on  a  certain  scale,  or  one 
full  size  and  the  other  to  a  certain  scale. 

As  soon,  however,  as  the  length  of  the  connecting 
rod  is  considered,  a  new  element  is  introduced,  inas- 
much as  that  the  divisions  or  scale,  while  still  serving 
to  denote  piston  positions  and  valve  movement,  will  not 
serve  to  denote  crank  pin  positions.  Thus,  in  Fig.  48,  we 
have  a  crank  pin  circle,  D,  I,  B,  and  an  eccentric  circle. 
d  b.  The  crank  pin  is  shown  at  G,  and  the  correspond- 
ing position  for  the  eccentric  center  is  at  g.  To  find 
the  position  of  the  valve  we  mark  the  dotted  line  / 

To  find,  however,  the  position  of  the  piston  we  must 
mark  the  center  line  A  B,  and  set  a  pair  of  compasses  to 
represent  the  length  of  the  connecting  rod  on  the  same 
scale  as  the  crank  pin  circle  D  B  is  drawn.  Thus,  if 


/•'/,/.  .is. 


for  example,  we  have  a  circle  whose  diameter  (1  inch)  is 
divided  into  sixteenths  of  an  inch.     Suppose,  then,  that 


this  circle  is  one-eighth  the  diameter  of  the  actual  crank 
circle,  the    compasses    must  be  set    to    one-eighth    the 


DIAGRAMS  FOR  DESIGNING    VALVE  MOTIONS. 


actual  length  of  the   connecting  rod.      Then  one  end   of 
tin'   •  !  is   rested  ai  tin- crank  jiin  center  (i  and  a 

mark  is   made    ai    M,     representing    the  center    of    the 
d    journal.       The    compasses  are  then     re-ted    at 
M.  and  an  arc.  (I    l',  is   drawn,  the  point   1'  rcpresei: 
the   position  of  the    piston  when  .1  <;. 

the  oilier    hand,    to  lind   the    position    of  tin1  d 
pin    from     that     of   the    piston    we     proceed    as     foil.. 

Suppose  the  piston  is  at  < ',  or  at    mid-stroke,  then  the 
at  (.'  and    point    (  >   is   marked.      Then 

from  i  >  a-  a  center,  arc  ('  S  is  drawn,  and  S  is  the  posi- 
tion of  the  crank  pin  when  the  piston  is  at  ( '. 
variation  between  the  crank  pin  and  piston  position  is. 
•  •fore,  represented  by  the  distance  between  point  S 
and  point  I.  Similarly,  when  the  piston  is  at,  H  the 
crank  pin  is  at  II,  as  is  shown  by  the  arc  II  R. 

Now.  let  it  In-  noted  that  since  the  crank  and  eccen- 
tric are  :'  the  same  shaft,  ami  therefore  revolve 
together,  they  may  be  represented  bv  a  two-armed  lever 
or  bell  crank,  as  denoted  in  Fig.  4!l  bv  a  thick  line  from 
(',  to  C  and  from  C  tog,  and  that,  this  being  the  case, 
we  are  enabled  from  the  position  of  one  to  find  the 
position  of  the  oilier,  whether  the  crank  pin  and  eccen- 
tric center  circles  are  drawn  to  the  same  scale  or  not. 

In  Kig    I'J.  for  example,  it  is  supposed  that  the  crank 


Fiy.   49. 

pin  stands  at  G  and  the  eccentric  center  at  g,  and  it  is 
required  to  find  where  the  eccentric  center  will  stand 
when  the  crank  pin  has  moved  to  position  H.  To  do 
this,  we  set  a  pair  of  compasses  to  the  radius  from  G  to 
•j.  and  then,  resting  one  point  at  H,  mark  the  arc  h,  and 
where  A  cuts  the  inner  circle  is  the  new  position  for  y. 

If   we  wish  to  find  how  much  the  valve   has  moved 
5 


from  its  mid-positi >\er  the  ports,  wo  drop  a  perpen- 
dicular 1,1.  and  get  po  .1  from  n  to  C  is  the 
amount  or  distance  the  valve  has  moved  from  mid- 
travel. 

It  now  remain^  io  show  that  the  circle  used  for  the 
path  of  the  crank  pin  can  just  as  well  be  used  for  the 
path  of  the  center  of  the  eccentric  as  not,  and,  there- 
fore, that  the  inner  circle  can  be  dispensed  with.  Sup- 
pose, then,  that  the  crank  pin  started  from  D  and  has 
arrived  at  <l.  and  the  center  of  the  eccentric  will  beat 
//.  and  the  valve  will  have  moved  three-quarters  of  its 
whole  travel,  or,  in  other  words,  the  amount  of  its 
motion  from  the  end  of  its  travel  is  from  d  to /  which 
is  three-quarters  of  its  whole  travel  from  d  to  b.  In- 
stead, however,  of  letting  the  inner  circle  represent  the 
path  of  the  center  of  the  eccentric,  suppose  that  the 
outer  circle  does  so,  and  we  may  prolong  the  throw 
line  of  the  eccentric  so  that  it  runs  from  C  to  P.  The 
diameter  of  the  outer  circle  will  then  represent  the 
valve  travel,  anil  to  find  where  the  valve  stands  we 
draw  a  lino  K,  giving  us  the  point  e,  distant  from  D 
three-quarters  of  the  diameter  of  circle  D  B  ;  hence  we 
find  that  the  valve  has  traveled  three-quarters  of  its 
stroke,  whether  measured  on  the  inner  or  on  the  outer 
circle  ;  hence  the  outer  circle  is  a  perfect  substitute  for 
the  inner  one. 

We  have,  in  this  case,  found  the  position  of  the 
eccentric  center  from  that  of  the  crank  pin  ;  but  sup- 
pose that  we  have  an  engine  whose  piston  travel  is  12 
inches,  length  of  connecting  rod  24  inches  and  valve 
travel  2  inches,  and  we  may  find  the  position  of  the 
piston  for  any  given  position  of  crank  pin  as  follows: 

In  Fig.  50  is  a  circle  of  an  inch  diameter,  and,  there- 


Fig.  50 

fore,  equal  to  one-twelfth  the  piston  stroke,  while  it  rep- 
resents half  the  valve  travel.     Let  the  crank  pin  be  at 


36 


position  G  and  the  eccentric  center  at  g,  and  setting  a 
pair  of  compasses  to  a  radius  of  2  inches,  so  as  to  rep- 
resent the  length  of  the  connecting  rod  on  the  same 
scale  as  the  diameter  of  the  circle  represents  the  piston 
travel  (that  is,  one-twelfth  full  size),  we  rest  one  point 
on  the  line  A  B  (representing  the  center  line  of  the 
engine),  and  mark  the  arc  G  P,  and  P  is  the  position  of 
the  piston  when  the  crank  pin  is  at  G  and  the  valve  is 
at/.  Now,  suppose  the  crank  pin  is  at  H,  and  we  may 
find  the  corresponding  piston  position  by  a  similar  pro- 
cess, as  is  shown  in  the  figure  by  dotted  lines. 

The  effect  of  this  variation  between  the  position  of 
the  crank  pin  and  that  of  the  piston  is  shown  in  Fig. 
51,  in  which  it  is  supposed  that  the  point  of  cut-off  is 


ir 

a 

r' 

) 

I 

^X  n™*> 

'_    | 

mechanism  is  so  constructed  that  the  cut-off  occurs  at 
equal  points  of  crank  movement,  it  will  occur  at 
unequal  points  of  piston  movement ;  and,  conversely,  if 
it  occurs  at  equal  points  of  piston  motion,  it  will  occur  at 
unequal  points  of  crank  motion.  The  position  of  the 
valve  is  .  represented  at  the  top  of  the  figure  on  the 
small  circle,  '/  1>.  (this  circle  representing  the  full  valve 
travel)  at  point  /,  the  valve  having  moved  from  l>  to  /, 
which  is  equal  to  the  width  of  the  port. 

It  is  obvious  that  the  angularity  of  the  valve  rod  will 
vary  the  motion  of  the  valve  in  the  same  manner  as 
the  angularity  of  the  connecting  rod  varies  that  of  the 
piston,  but  the  length  of  the  valve  rod  is  usually  so 
great  in  proportion  to  the  valve  travel  that  the  error  is 


for  one  stroke  at  G  and  for  the  other  at  H.  The  valve 
position,  when  the  crank  pin  is  at  G,  must  be  as  shown 
at  the  top  of  the  engraving,  the  valve  traveling  as  de- 
noted by  the  arrow  and  port  x  being  closed.  The  cor- 
responding piston  position  is  shown  in  the  cylinder  at 
P',  and  also  within  the  circle  at  P,  the  distance  from  N 
(representing  the  beginning  of  this  stroke)  to  P'  in  the 
cylinder  being  the  same  as  from  D  to  P  measured 
across  the  circle,  and  it  is  seen,  that  while  the  crank  has 
moved  three-fourths  of  its  stroke  the  piston  has  moved 
more  than  thi-ee-fourths  of  its  stroke. 

Similarly,  when  the  crank  pin  is  at  H,  and  has  moved 
three-quarters  of  the  distance  from  B  to  D,  the  piston 
will  be  at  R,  and  has  traveled  less  than  three-fourths 
of  its  stroke,  and  it  becomes  evident  that  if  the  valve 


too  minute  to  have  any  practical  or  appreciable  import- 
ance, and  may  therefore  be  discarded. 


Fig.  52. 

Now,  suppose  we  have  a  valve  mechanism  in  which 
the  valve  has  neither  lap  nor  lead,  and  that  the  circle 


DL\  '//,'.  l.l/.v  l-'Ol! 


,    VALVE 


37 


vii  iii    Fig.   .">-.    rt'i  :  •'  path  nt  iln1  center  of 

.-(•(•.•ntric  drawn   full  si/.e.  and  al-o   the   path  o 
.k   jiin   drawn  tn  BO  &y,   iiiif-ii'iith  full 

.Ive  lias  in)  la]),  tin'  throw  line  of  tlir 
eccentric  uill  stand  at  a  right  angle  or  angle  of  90°  to 
the  crank.  Suji|K)se  the  crank  stands  at  II  ( '.  and 

:itric  will   stand  at  ./.    it-   throw   line    being  at    I    i 
which  is  at  a   right   angle  to  the  crank.      As  • 
trie  and  crank  are  last  on  the   same  shal'l.  the    length  of 

d  over  by  both  will  lie  ei|iial   in  eijiial  - 
time;   thus,  while  crank   Jiin  II   moves   to   I'.,  the  eccen- 
er  will  move   from   z   to  //.  are  x  //   Keing  equal 
in  length  to  arc  ]  I   I!. 

Now.  su]i]«)se  that  instead  of  the  valve  having  no 
lap.  and  the  live  steam  following  the  jiiston  (liiring  its 
full  stroke,  it  is  required  that  when  the  crank  pin  is  at 
It  the  steam  is  to  lie  cut  otT.  ami  the  remainder  of  the 
ike  is  to  lie  performed  with  the  steam  already  in  the 
cylini  £  expansively,  and  then  the  arc  ./•  //  i 

lie  passed    over  by  tl cceiitric   after  the  steam  valve 

closes  the  steam   port   and  cuts  off  the  steam   supply  at 

';ead  end  of   the  cylinder  (the  end  furthest  from  the 

crank  l>eing    termed    the    head    end    of    the    cylinder). 

Hence,  during  that    part  of  the  eccentric  motion  from 

//.  the   valve   must  have  lap  enough   to  keep  the 

port  closed  at  Imth  its  steam  and  exhaust  edges,  so  that 

s-team  ran  neither  get  into  nor  out  of  the  cylinder. 

given  amount  of  eccentric  motion  gives  more 
motion  to  the  valve  in   proportion  as  the  throw  line  of 
the  eccentric  is  nearer  to    its  mid-position  //,  therefore. 
instead  of  leaving  the  eccentric  (as  at*)  at  an  angle  of 
I1'!    to  the  crank,  or  66°  from  its  mid-position,  suppose 
In'  given  an  angular  advance  equal  to  one-half  the 
i/.  or  ;i:;0,  in  which  case  when  the  crank  pin  is  at 
11.   the   eccentric  will  be   at  h.     When,  therefore,   the 
crank  lias  moved  to  B  (at  which  time  steam  is  to  be  ad- 
mitted to  the  other  steam  port)  the  eccentric  will  have 
moved  to  /,  and  will  stand  at  33°  ahead  of  its  mid-posi- 
tion )/.     Thus  it  will  !>e  seen  that,  although  the  length 
arc    li    !'.  traveled  over  by   the   eccentric    while    the 
:n  ]Kirt   is  closed,  still  equals  in  length  the  arc  H  R, 
traveled  over  by  the  piston  during  the  period  of  expan- 
ig    the  eccentric  ahead,  giving   it  the 
angular   advance    from  x  to  h,   its  motion,  during  the 
|M-r;od  of  expansion,  has  been  brought  equally  on  each 


it  to  move  tho  valve  quicker  and  to 
greater  amount  of  motion  while   it  is  acting  to 
cut  oil  the  steam   for  the  port  at  one  port,  and  travel- 
ing to  open  the  other  for  admission. 

114.  .">::,  in  which  H  represents  the  posi- 
tion .  nik  pin  at  the  point  of  cut-off,  and  /*  the 
jKisition  of  the  eccentric  at   the  same  instant,  then  from 
,1  to  1>  re  ie  amount  of  valve  travel  that  occurs 
li\e  steam  is  cutoff,  and   from  d  to  C  represents 
;, mount  of  valve    lap   required  to   cutoff  when  the 
crank  pin  is  at  II    and  the  pi-ton  is  at  R.     Similarly  for 
tho  other  stroke,  the  crank  pin  starting  from  B,  the  dis- 


Fig.   53. 

tance  from  C  to  e  represents  the  amount,  of  lap  the 
valve  must  have  to  cause  the  steam  to  be  cut  off  when 
the  crank  has  arrived  at  a  point  exactly  opposite  to 
H.  In  this  construction  we  have  found  at  h  the 
eccentric  position  for  crank  position  H,  and  then  moved 
them  around  the  circle  at  the  same  distance  apart,  just 
as  though  we  were  moving  a  two-armed  lever  on  the 
center  C.  But  we  may  move  the  eccentric  back  from  h 
to  H,  thereby  making  H  represent  both  the  crank  and 
the  eccentric  at  the  same  time,  and,  in  this  case,  all  the 
points  and  lines  on  the  diagram,  that  relate  to  the  eccen- 
tric and  valve,  would  be  turned  back  to  the  same 
amount.  Therefore,  if  h,  Pig.  53,  becomes  H,  Fig.  54, 
then  b,  Fig.  53,  will  become  B  in  Fig.  54,  and  the  point 
of  mid-eccentric  travel  ;/  will  be  midway  between  II 
and  B,  or  y,  Fig.  54.  So,  likewise,  the  line  y  C,  Fig.  53. 
will  become  i/  C  in  Fig.  54.  Now  the  line  on  which 
the  travel  of  the  valve  is  shown  must  be  at  a  right  angle 
to  tho  line  y  C,  ar.d  is,  therefore,  shown  in  Fig.  54  by 
the  line  v  V.  and  the  lines  H  d  and  b  e  (corresponding 
to  lines  /(  d  and  b  e  in  Fig  53)  may  be  drawn,  giving  in 
their  distance  apart  the  total  amount  of  lap,  one-half, 


38 


MODERN  STEAM  EXG1XES. 


as  d  C,  being  for  one  port,  and  the  other,  C  e,  serving 
for  the  other  port. 

Thus  the  movements  of  piston,  crank  and  valve  may 
be  shown  on  the  diagram,  the  position  of  the  piston  for 
any  position  of  crank  being  shown  on  the  line,  BCD, 


Fig.   54. 

as  before,  while  the  positions  of  valve  corresponding  to 
those  of  the  eccentric  may  be  shown  on  the  line  V  C 
v.  But  it  must  be  borne  in  mind,  that  while  B  i  D  is 
the  line  of  motion  relating  to  the  crank,  line  V  v  is 
that  relating  to  the  valve  motion,  and  that  this  line 
stands  at  the  same  angle  to  the  line  B  C  D  for  piston 
travel  that  the  eccentric  is  in  advance  of  the  crank. 
Thus,  in  Fig.  54,  V  C  is  at  an  angle  of  1 23°  from  the 
crank  II  C,  and  hence  represents  an  angular  advance  of 
eccentric  amounting  to  33°,  because  without  angular 
advance  the  eccentric  would  stand  at  90°,  and  123°  less 
90°  is  33°. 

In  Fig   55,  we  have  a  diagram  constructed  upon  the 


0       2       4       676 

Scale  of  intJtF* /or  ptettm  travel 
(Wttraed.  ) 


Fig.  55. 

foregoing  principles,  this  particular  form  being  that  em- 
ployed by  Mr.  J.  ~W.  Thompson,  of  the  Buckeye  Engine 


Works.  The  circle  is  drawn  to  a  diameter  equal  to  the 
full  travel  of  the  valve,  which  is  the  most  convenient, 
although  it  is  obvious  that  the  larger  the  circle,  the  more 
accurate  are  the  results  obtained.  The  piston  stroke 
being,  iii  this  example,  14  inches,  a  scale,  equal  in  length 
to  the  diameter  of  the  circle,  is  constructed  below  it. 
Now,  suppose  a  slide  valve  is  to  be  designed  which  will 
cut  off,  say,  at  three-quarters  stroke,  and  do  so  equally 
on  both  strokes,  then  set  off  on  line  B  D,  a  point  P 
three-fourths  of  the  diameter  of  the  circle  distant  from 
B,  and  set-off  R  three-fourths  of  the  distance  from  D  to 
B,  then  P  and  R,  will  represent  the  piston  positions  at 
the  points  of  cut-off.  With  compasses  set  to  represent 
the  length  of  the  connecting  rod — in  this  case  2.}  times 
the  diameter  of  the  circle — mark  arcs  P  G  and  R  II, 
locating  at  G  and  H  the  corresponding  crank  pin  posi- 
tions. From  H  draw  the  line  H  D,  meeting  the  circle 
exactly  at  D,  if  the  valve  is  to  have  no  lead  at  the  head 
end  of  the  cylinder,  (the  head  end  being  represented  !iy 
end  1)  of  the  line  B  C  I)). 

Xo\v,  since  the  admission  is  to  occur  when  the 
piston  and  crank  are  at  the  beginning  of  this,  which  wo 
may  term  the  forward  stroke,  and  steam  is  to  be  cut  off 
at  II,  then  the  crank  must  pass  over  that  part  of  the 
circle  lying  between  D  and  H,  while  the  port  at  the 
head  end  is  open. 

Now,  since  the  same  point  is  taken  to  represent  the 
eccentric  and  the  crank,  therefore  when  the  eccentric  is 
at  D,  the  edge  of  the  valve  is  moving  away  from  the 
steam  edge  of  the  port  to  open  it,  but,  by  the  time  the 
crank  has  arrived  at  H,  the  edge  of  the  valve  will  have 
first  moved  over  the  port,  leaving  it  full  open,  and  then 
moved  back  again  to  close  it,  just  closing  it  at  the  time 
that  the  crank  has  reached  point  II ;  hence  the  line 
v  V,  drawn  through  the  center  C  and  at  right  angle  to 
H  D,  will  divide  the  arc  D  V  H  equally,  and  that  part 
of  the  arc  from  D  to  V  will  represent  the  period  during 
which  the  valve  is  traveling  to  open  the  port,  while  the 
part  from  V  to  H  will  represent  the  period  during  which 
the  valve  is  traveling  to  close  the  port  and  effect 
the  cut-off ;  hence  V  v  represents  a  center  line  on 
which  the  valve  is  moving  and  on  which  the  posi- 
tions of  the  valve  at  any  point  of  the  stroke  may 
be  located  and  on  which  all  laps  and  leads  must  bo 
laid  out.  The  point  C,  of  course,  still  represents  the 


UEStQNINQ    \'A/.\'H  .l 


tin-  viilvo  travel,  and  a  line,  drawn  through  <  ' 

and  •  \"r.  locates  liiu1  y  .:.  \vliicli.  rela- 

|y    M    line    \    '•.    i<   tin'    point  of  mid-travel   of  the 

To  liml  tin1  amount  of  valve  lead  necessary  to  In- 
tin'  valve  at  tin'  crank  mil.  in  nnler  to  equal- 
i/e  the  ]ioint  of  cut-oil  for  the  two  piston  strokes,  draw 
the  line  (',  A  parallel  to  line'  I>  II.  Tin-  amount  to 
which  end  A.  of  line  (i  A.  falls  In-low  1!  (that  is.  dis- 
tance A  It)  is  the' required  amount  of  lead.  This  will 
appear  mi  applying  similar  ivaMiniiig  to  that  already 

•n  when  supposing  that  if,  on  the  return  stroke,  tin- 
valve  at  the  crank  end  opens  when  the  piston  and  crank 

•it   1'..  then — as  motion  occurs  in  the  directi if  the 

arrow — when    theeccenlric    has    reached    its  center   line 
V    r.   and    is  at  a,    the    valve   will    begin    to   close,    and 

.Id  finally  close   when  the  crank   and  eccentric  lire  at 

the  distance  /    B,  from  /•,  or  at  point   X.  corresponding  to 

position  of    ,-,    which  is   too  soon,  as  the   piston 

;id  have  reached   1'.  and    the  crank    have    reached   G, 

to  reach  that  result  admission  must  begin  when  the 
crank  is  at  A.  thus  making  the  length  of  arc  A  i>  equal 
to  i-  (!.  in  onler  that  the  point  of  cut-otT  may  not  occur 
until  the  crank  reaches  < !. 

It  will  In-  seen  that  to  equalize  the  points  of  cut-off, 
then,  it  has  Keen  found  necessary  to  j;ive  lead  at  the 
port  nearest  to  the  crank,  that  being  the  port  which 

:ves  steam  when  the  crank  is  at  B,  and  that  there  is 
no  valve  lead  at  the  other  port  which  corresponds  to 
the  end  I)  of  the  piston  travel.  Had  we  commenced 
at  the  other  stroke  and  drawn  G  A  first,  letting  it  meet 
the  point  11.  then  by  drawing  line  D  H  parallel  to 
0  \.  I)  II  would  cut  the  circle  below  D,  showing  nega- 
tive lead,  or,  in  other  words,  that  port  would  not  have 
opened  until  the  piston  had  passed  the  dead  center  D 

i  reached  the  line  H  D.  Or  line  B  G  might  be 
drawn  to  give  negative  lead  at  both  ends  by  simply 
drawing  it  from  point  G  to  a  certain  amount  above  the 
point  B.  and  then  by  drawing  line  H  D  from  H  to  a 
point  as  much  below  D  as  A  was  drawn  above  B,  there 
would  lie  equal  negative  lead  at  both  ends,  either  nega- 
tive lead  or  else  unequal  lead  being  the  price  that  must 
be  paid  for  equalizing  the  point  of  cut-off  by  employing 
unequal  lap.  Obviously,  however,  the  amount  of 
inequality  of  lead  induced  by  the  unequal  lap  is  repre- 


39 


sented  liy  the  length  of  arc  from  A  to  H,  and  we  may 
throw  this  all  at  one  end.  as  in  the  figure,  or  divide  it 
between  the  two  ends  as  [Hiinted  out. 

\\'e  may  now  provide  for  the  point  of  release  and 
the  point  at  which  compiv^ion  is  to  take  place.  Let  it 
In-  required,  then,  that  the  compression  shall  begin 
when  the  piston  is  within,  say.  IJ  inches  of  the  termi- 
nation of  the  stroke,  and  we  set  olf.  on  the  line  of  piston 
travel,  points  ,1  and  L,  distant  from  points  B  and  D  IJ 
inches,  according  to  the  scale  of  piston  travel.  From 
these  two  points,  with  compasses  set  to  represent  the 
length  of  the  connecting  rod.  we  draw  the  arcs  L  land 
J  /.  locating  the  corresponding  crank  pin  positions  I  and 
/.  From  /  draw  \\nej  k  parallel  to  H  D,  and  with  com- 
passe-;  set  to  represent  the  connecting  rod  length,  draw 
arc  /.•  K.  locating  point  of  exhaust  K. 

For  the  point  of  exhaust  on  the  other  stroke,  draw 
from  point  /,  line  /  m,  parallel  to  II  D,  and  from  m, 
with  the  compasses  set  as  before,  draw  arc  m  M,  loca- 
ting the  point  M  where  the  exhaust  is  to  begin.  The 
reason  that  the  line  j  k,  drawn  from/  or  the  point 
where  the  crank  is  when  compression  commences  on 
the  crank  end  of  the  cylinder,  locates  the  point  k  where 
the  crank  is  when  the  exhaust  begins  at  the  same  end, 
that  is,  supposing  the  crank  to  be  at  /  and  the  eccen- 
tric at  the  same  point,  the  compression  is  commencing 
with  the  eccentric  lacking  distance  j  y  of  being  at  mid- 
throw  ;  hence,  as  the  same  edge  of  the  valve  that  closes 
the  port  for  compression  on  one  stroke,  opens  for  the 
exhaust  on  the  other  stroke,  the  eccentric  must  reach, 
on  its  return  stroke,  the  same  distance/  y  p<tst  the  oppo- 
site mid-position  Z,  or,  in  other  words,  reach  the  point  K. 

Now,  since  line .  V  v  represents  the  line  of  travel  of 
the  valve,  Y  and  Z  represent  the  mid-throw  positions 
of  the  eccentric,  and  C  the  mid-position  of  the  valve, 
and  starting  out  with  a  valve  having  no  lap  when  the 
eccentric  and  crank  are  at  H,  line  Y  Z  representing 
mid-throw  of  eccentric,  then  the  valve  would  be  the  dis- 
tance d  C  from  mid-position  ;  hence,  exhaust  lap,  equal 
in  amount  to  radius  d  C,  would  be  required  for  the  port 
at  the  head  end  in  order  to  close  it. 

Likewise,  when  compression  is  to  begin  at  the  crank 
end.  with  the  eccentric  and  crank  at  /,  or  distance  /  y 
from  mid-throw,  the  exhaust  edge  of  the  valve  would 
be  the  distance  p  C  from  the  exhaust  edge  of  the  port, 


40 


y  .S77-.MJ/   K 


and  exhaust  lap  equal  to  distance  p  C  would  have  to  be 
given  to  the  crank  end  of  the  valve.  Similarly,  with 
the  cut-off  at  G  and  compression  at  ?,  exhaust  lap,  equal 
to  distance  r  C,  would  be  required  on  the  head  end  of 
the  valve.  To  summarize  the  data  thus  arrived  at,  we 
have,  in  Fig.  55,  C  a  as  the  steam  lap  at  the  crank  end, 
and  C  d  that  at  the  head  end,  while  0  p  and  C  r  are  the 
corresponding  exhaust  laps,  all  these  measurements 
boing  taken  on  the  line  V  v,  the  lesser  amount  of  ex- 
haust lap  (C  r),  it  will  be  noticed,  belonging  to  that  port 
of  the  valve  that  has  the  most  steam  lap. 

The  angular  advance  of  the  eccentric  is  equal  to  arc 
V  i  or  32°,  but,  for  practical  purposes,  it  is  more  con- 
venient to  express  it  in  terms  of  the  amount  the  valve 
is  displaced  from  its  mid-travel  when  the  crank  is  on  its 
dead  center.  This  amount  is  found  by  measuring 
from  v  to  line  t  C  in  a  parallel  direction,  and  is  shown 
in  Fig.  55  to  be,  in  this  case,  |J.  inch. 

The  amount  of  steam  lap  being  greater  for  one  port 
than  for  the  other,  it  is  obvious  that,  in  order  that  both 


letters  of  reference.  It  is  assumed  to  be  at  mid-travel, 
at  which  position,  alone,  will  the  laps,  as  obtained  from 
the  diagram,  show  in  their  proper  amounts.  To  draw, 
or  lay  out,  such  a  valve  from  the  diagram,  draw  the  line 
A  B,  representing  the  face  of  the  valve  and  of  the 
ports,  and  draw  the  inside  edges  C  of  the  cylinder  ports 
equi-distant  from  the  center  of  the  cylinder  exhaust 
port.  Next  draw  the  width  of  ports  P  P;  the  valve 
length,  without  any  steam  lap,  would  then  bo  X  added 
to  P  P,  or  distance  W.  Steam  lap  C  </,  corresponding 
to  C  (/  on  the  diagram,  may  then  be  marked  for  the 
head  end  of  the  valve,  and  similar  lap  a  C  at  the  crank 
end.  Also  exhaust  laps  C  p  and  r  C  (corresponding  to 
C  p  and  r  C  on  the  diagram)  may  then  be  drawn.  As 
the  lip  H  of  the  valve  (corresponding  to  the  width  of 
the  port  plus  the  laps  d  r  in  Fig.  55)  is  wider  than  lip 
L  (corresponding  to  a  p  in  Fig.  55),  it  is  important  that 
the  valve  be  placed  the  proper  end  foremost,  as,  wen; 
end  B  placed  nearest  to  the  crank,  the  points  of  cut-off, 
compression,  etc.,  instead  of  being  equalized  by  the  un- 


Fig.   56. 


ports  may  open  full  for  the  admission  of  steam,  the 
width  of  port  should  equal  the  greater  amount  of  steam 
lap,  or,  in  this  case,  C  d,  assuming  average  conditions 
as  to  speed,  load  and  pressure,  etc.  In  other  words,  it 
is  assumed  that  the  area  of  steam  port  has  been  deter- 
mined as  that  most  desirable  for  the  average  conditions 
under  which  the  engine  is  to  run,  and  if  thia  area  is 
altered,  then  the  other  elements  of  the  diagram  must 
be  proportionally  altered.  Thus,  the  width  of  port  has 
been  taken  as  equal  to  distance  v  a;  but  suppose  that 
this  was  afterward  considered  insufficient,  and  a  greater 
port  width  be  used,  then  the  travel  of  the  valve  must 
be  proportionally  greater,  as  also  must  the  laps. 

In  Fig.  56  we  have  a  valve    with    the    proportions 
arrived  at  from  the  diagram,   and   with  corresponding 


equal  laps,  would  be  distorted  worse  than  would  be  the 
case,  if  the  laps  were  made  equal.  This  fact,  together 
with  the  excessive  lead  inequality,  leads  to  the  consider- 
ation of  other  plottings,  in  which  cut-off  equalization  is 
abandoned  either  wholly  or  in  part. 

Thus,  in  Fig.  57,  having  located  points  of  cut-off  at 
P  and  R,  perpendiculars  P  G  and  R  H  are  drawn,  loca- 
ting the  corresponding  crank  pin  positions,  supposing 
the  length  of  the  connecting  rod  to  be  infinite,  or, 
rather,  leaving  it  out  of  the  question.  Line  II  1 )  is 
then  drawn,  and  line  G  B  (corresponding  to  Line  G  A  in 
Fig.  55)  parallel  to  H  D,  and  passing  exactly  through  B 
(instead  of  below  it,  as  in  Fig.  55),  thus  showing  equal 
lead,  or,  rather,  no  lead  at  either  end.  From  points  ,1 
and  L,  where  it  has  been  determined  that  the  compros- 


I>IM;I:.\MS  roi:  DESIGNING  VALVE  .\mrio\s. 


41 


sion  is  to  begin,  nnd  with  tho  c<>  -i  to  tepp 

the  length  of  the  connecting  rod,  strike  act  i-'-ating 
/and  /,  and  proceed  ;it  was  explained  with  reference  to 
Fig.  55,  all  jioints  being  similarly  lettered  in  the  two 


Here,  then,  the  lead  and  compression  are  equalized 
for  the  two  strokes  while  the  exhaust  is  nearly  equal- 
-  drawn  through  II  and  G,  giving  points   x 
,'iud  //  where  the  piston   will  actually  lie  when  the  cut- 
oil  occurs,  thus  giving  an  inequality  of  It  »  at  oneend, 
and   I'  j-  at  the  otlier.  or  both  together  equal  to  Px  of 
A  valve  mechanism  thus  proportioned  is  suit- 
•r  engines   in  which   the  cut-off  is  effected   by  a 
separate  valve  which  is  capable  of  independent  equali- 
sation,  in  which  case  the  inequality  in  the  points  of 
liy  the  main   valve  is  of  no  consequence,  since 
•  •ted  by  the  cut-off  valve.     In  this  case, 
and  a  p  are  of  unequal  width,  but  that 
i  to  the  crank  (C  «,  Fig.  .">(!)  is  the  widest.     This 
from  the  fact  that  the  exhaust  lap  is  added  at 
C  p  to  equalize  the  compression,  while  no  excess  of  lead 


Fig    58. 

has  been  given  at  A  to  equalize  the  points  of  cut-off ; 
hence,  this  valve  also  requires  to  be  placed  the  proper 


end  and    since  it  is   generally  prcf. 

have  equal  lead  at  each  port,  the  only  way  to  secur 
the  same  time  equal  compression  is  to  provide  it  in  the 
manner  here  shown  in  Fig.  ">7. 

If  the  valve  is  to  have  equal  lips,  so  that  it  may  be 
turned  end  for  end  on  its  seat,  and,  therefore,  cannot  be 
put  on  wrong  end  foremost,  it  may  be  plotted  as  shown 
in  Figs.  .Vs  and  .">!».  Fig.  58  is  constructed  in  the  same 
way  as  Fig.  57,  the  compression  being  equalized  be- 
cause J  and  L  are  equi-distant  from  B  and  D  respect- 
ively. Hut  since  the  width  of  lip  of  any  valve  is  equal 
to  the  width  of  the  steam  port  plus  the  amount  of 
steam  and  exhaust  lap,  therefore  the  lip  of  valve,  de- 
signed as  in  Fig.  57,  would,  at  end  furthest  from  crank, 
be  width  of  steam  port  plus  exhaust  lap  C  r  and  steam 
lap  C  d ;  and  at  crank  end  would  be  width  of  port  plus 
exhaust  lap  C  r  and  steam  lap  C  a.  Now,  suppose 
enough  to  be  cut  off  C  a  to  make  both  lips  of  equal 
width,  and  the  construction  is  shown  in  Fig.  59,  in 
which  a  (corresponding  to  a,  Fig.  58)  has  been  made 


Fig.  59. 

the  same  distance  from  p  that  d  is  from  r  in  the  same 
figure,  thus  making  a  p  equal  to  r  d  (or  lip  H  equal  to 
lip  L  in  Fig.  58).  A  G  is  parallel  to  H  D  as  before, 
but  is  drawn  through  a,  bringing  point  G  further 
around,  thus  changing  the  motion  of  the  piston  at  the 
point  of  cut-off  from  x,  Fig.  57,  to  x,  Fig.  58.  It 
will  be  observed  that  the  distance  from  B  to  n,  Fig. 
58,  is  very  nearly  the  same  as  that  from  D  to  x,  show 
ing  that  the  cut-off  is  nearly  equalized,  that  the  com- 
pression is  equalized,  that  the  exhausts  are  good  and 
the  lead  inequality  is  only  about  half  that  shown  in 
Fig.  56  at  B  A.  The  valve  is,  therefore,  symmetrical, 
and  effects  a  compromise  between  the  excessive  lead 
inequality  of  Fig.  56  and  the  great  cut-off  inequality 
of  Figs.  57  and  58,  and,  but  for  the  objection  that  the 


42 


MODERN    STEAM    ENGINES. 


unequal  lead  would  be  too  apt  to  be  taken  as  a  defect, 
it  would  constitute  the  best  arrangement,  as  a  whole, 
that  could  be  made. 

DH.   ZEUXEK'S  VALVE  DIAGRAM. 

The  principles  upon  which  the  foregoing  diagrams 
are  constructed,  are  derived  from  the  form  of  diagram 
invented  by  Dr.  Zeuner,  and,  in  order  to  further  ex- 
plain the  base  upon  which  such  diagrams  are  plotted,  it 
it  may  be  as  well  to  trace  out  the  path  of  the  crank  pin 
in  connection  with  the  valve  positions  at  the  time  the 


From  these  dimensions  it  is  required  to  find  the  posi- 
tions of  the  crank  and  eccentric  for  the  various  events 
during  the  stroke,  and  this  may  be  done  as  follows  : 

Let  the  dotted  circle  in  Fig.  60  be  4  inches  in  diame- 
ter, representing  the  stroke  of  the  valve  drawn  full  size 
and  the  piston  stroke  one-fifth  full  size,  and  its  circum- 
ference will  represent  the  path  of  the  center  of  thh 
eccentric  drawn  full  size  and  the  path  of  the  crank  pin 
drawn  one-fifth  full  size.  Now  suppose  the  crank  to 
be  on  the  dead  center  B  and  to  require  to  move  in  the 
direction  denoted  by  the  arrow.  Suppose  the  valve  was 


\ 


\ 


\ 


events  of  cut-off,  etc.,  occur.     Suppose  then,  that  the 
engine  has  the  following  proportions  : 

Length  of  piston  stroke  20    in. 

Width  of  steam  ports     —  —       1 

Steam  lap  1 

Lead  at  head  end 

"      "  crank  end      - 

Travel  of  valve  —  —        —       4 


placed  in  its  mid-position,  as  in  Fig.  M,  and  the  throw- 
line  of  its  eccentric  would  stand  on  the  line  C  M  in 
Fig.  60.  As  the  port  a,  Fig.  M,  is  the  one  that  must 
be  open  to  the  amount  of  the  lead  when  the  crank  is  at 
B,  Fig.  CO,  and  as  the  amount  of  the  lead  is  given  for 
this  port  as  being  ^  in.,  the  valve  must  be  moved  to  thp 
right  to  the  amount  of  the  lap  and  the  lead,  or  1|  in. 


i>l.\<ii;.\.Ms  /••<>/{  DESIGNING    VALVE  M»r/o\s. 


43 


T'>  tind   the  jiosition  of  tin-  eccentric  when   tin-  valve 

is  thus  moved  to  l'»r  tin'  lead,  we  mark  a  poim 

g  c.il.  di.-tant    I' re  mi  ('   to  the  amount    of    1  J  inches 

(lap  1   inch.  lea>]  at  this  end   i)  and  erect  a  perpendicular 


ffff.    .I/, 
line  from  s  to  V.      We  then  draw  a  line   from   V  to  C, 

and  this  will  represent  the   throw    line   of  ihi entric 

with  the  valve  open  to  the  amount  of  the  lead  and  with 
'•entrie   in   the  position  it   must  occupy  when   the 


61. 

rrank  is  on  its  dead  crater  R.  This  line  V  C  is  shown 
drawn  on  the  eccentric  in  Fig.  61,  V  representing  the 
center  of  the  eccentric  and  C  the  center  of  the  crank 


/•'/</.    V. 

The  position  of  the  valve  when  the  crank  is  at  B, 
Fig.  GO,  and  the  eccentric  at  C  V,  is  shown  in  Fig.  V, 


in  which  the  valve  and  ports  are  shown  one-quarter 
full  si/e,  the  port  n  lieing  open  to  the  amount  of  the 
lead.  We  may  now  trace  the  events  throughout  the 
stroke  as  follows: 

Suppose  the  eccentric  to  have  moved  from  V  to  I'. 
Fig.  IpO.  and  it  will  have  arrived  at  the  end  of  its  stroke, 
leaving  the  port  «  full  open,  as  in  Fig.  1  >.  To  find  the, 
-pond  ing  position  of  crank,  we  may  seta  pair  of 
compasses  to  the  radius  li  Y.  Fig.  60,  and  resting  one 
point  at  1)  (where  the  eccentric  is)  mark  an  arc  G, 


Pig.   D. 

and  a  line  from  G  to  C  will  represent  the  crank  posi- 
tion.  The  eccentric,  after  leaving  position  I),  begins  to 
move  the  valve  hack,  and  when  it  has  arrived  at  X,  Fig. 
(iO,  will  have  moved  it  a  distance  equal  to  the  amount 
of  the  steam  lap,  thus  effecting  the  cut-off,  the  position 
of  the  valve  at  this  time  being  shown  in  Fig.  Z. 

The  point  Z  is  obtained  by  the  following  reasoning  : 
Suppose  the  valve  is  at  the  end  of  its  stroke,  as  in  Fig. 
D  (the  eccentric  being  at  D,  Fig.  60),  and  it  is  obvious 


Fig.  Z. 

that  it  must  move  to  the  left  to  an  amount  equal  to  the 
width  of  the  port,  or  in  this  case  an  inch,  before  it 
closes  the  port  a  and  effects  the  cut-off,  we,  therefore, 
mark  point  d  an  inch  from  D,  and  then  draw  the  verti- 
cal line  from  d  to  Z,  showing  at  Z  the  eccentric  posi- 
tion when  the  valve  is  in  the  position  shown  in  Fig.  Z. 
The  next  event  that  will  occur  is  for  the  port  a  to 
open  for  the  exhaust,  and  it  is  obvious  that  this  will 
take  place  when  the  valve  has  moved  from  its  position 


44 


MODERN    STEAM 


in  Fig.  Z  to  an  amount  equal  to  the  amount  of  the 
steam  lap  which  is,  in  this  case,  an  inch  ;  hence,  we 
measure  off  an  inch  to  the  left  of  d,  Fig.  60,  arriving 
at  C,  and  a  vertical  line  drawn  from  C  to  E  gives  us 
the  position  of  the  eccentric  which  is  then  in  mid-posi- 
tion, the  valve,  also,  being  in  mid-position,  as  in  Fig.  E, 
the  exhaust  being  about  to  open  for  port  a. 

The  next  event  will  be  that  port  a  will  bo  open  full 
as  an  exhaust  port,  and  to  do  this  it  must  move  an 
amount  equal  to  the  width  of  the  port  (an  inch),  we 
therefore  mark  e  an  inch  from  C,  and  draw  the  perpen- 


close  a  as  an  exhaust  port,  and  to  do  that  it  must  move 
back  to  an  amount  equal  to  the  width  of  the  port  (an 
inch),  passing  from  the  position  in  Fig.  B  to  the  posi- 
tion shown  in  Fig.  X.  To  find  the  corresponding  ec- 
centric position  we  mark,  on  Fig.  60,  an  inch  to  the 
right  of  B,  arriving  at  e,  and  a  line  e  X  gives  the  eccen- 
tric position  when  the  valve  is  in  the  position  in  Fig.  X 
and  port  a  is  about  to  begin  to  close  to  the  exhaust.  The 
next  event  that  will  occur  is  for  the  port  a  to  be  closed 
as  an  exhaust  port,  and  in  order  to  effect  this  the  valvn 
must  move  from  its  position,  in  Fig.  X,  to  its  mid-posi- 


dicular  line  e  Y,  which  is  the  position  of  the  eccentric 
when  the  port  a  is  open  full  for  the  exhaust,  as  shown 
in  Fig.Y.  Continuing  the  motion  and  considering  the 
port  a  only,  the  next  event  is  for  the  eccentric  to  move 
to  the  end  B  of  its  stroke  in  Fig.  60,  and  the  corres- 
ponding valve  position  is  shown  in  Fig.  B.  The  next 
event  is  for  the  valve  to  move  back  until  it  begins  to 


X 


tion,  as  in  Fig.  M,  the  distance  moved  obviously  equal- 
ing the  amount  of  the  steam  lap,  as  will  be  seen  on  in- 
specting the  two  figures. 

As  the  amount  of  steam  lap  is  an  inch,  and  C  is  an 
inch  from  e,  we  mark  a  vertical  line  C  M,  giving  at  M 
the  position  of  the  eccentric  when  the  valve  is  in  the 
position  shown  in  Fig.  M,  both  valve  and  eccentric 


/;/.l'.7M.I/.v  F»lt  />/-:sft;\/\(;    VALVE 


45 


in  mill-position.  The  j>ort  «  being  closed,  the 
conipr  u  n,  and  wu  have  found  tin-  aooeo 

y  event  during   this  stroke,   except 

.ink  ]>osition  at  the  time  tlie  valve  is  about  to 
open  for  the  lend,  and  this  \ve  may  find  from  the  follow- 
ing  reasoning  : 


When  tlie  eccentric  La  at  M,   Fig.  GO,  and  the  valvo 

in  mid-position,  as  in  Fig.  M,  it  will  require  to  move   to 

iount  of  tlie  steam  lap  in  order  to   bring  the  edge 

of  the  valve  coincident   with  the  edge  of  the  port,  as  in 


Fig.  7..  ready  to  open  for  the  lead,  and  the  amount  of 
steam  lap  being  an  inch  we  measure,  in  Fig.  GO,  an  inch 
from  the  line  M  C  and  arrive  at  d.  From  d  we  draw 
the  line  d  P,  giving  at  P  the  position  of  the  eccentric 


when  the  valve  is  in  the   position  in  Fig.  P,  and    the 
is  about  to  open  for  the  lead.     To  find  the  crank 
on,  we  set  the  compasses  to  the  radius  Ti  V  (the 
ndY  C,  representing  the  angle  of  the  eccen- 
tric to  the  crank,  or,  what  is  the  same  thing,   the  angle 
of  the  crank  to  the  eccentric),  and   from  P  as  a  center 


mark  an  arc  A.  and  from  the  point   where  this  arc  cuts 
the  dotted  circle  we  draw  a   lino  toC,    which   will    •_ 
the  position  of  the  crank   when  the  eccentric  is  at  P, 
Fig.  (if),  the  valve  in  the  position  shown  in  Fig.  P,  and 
tlie  port  n  about  to  open  for  the  lead. 

We  might  find  the  crank   pin  position   for  any  other 


M. 


eccentric  position  by  similar  means,  because  as  soon 
as  the  line  V  C  is  obtained,  we  have  found  the  position 
of  the  eccentric  with  relation  to  the  crank,  and  as  both 
are  fast  on  the  same  shaft  their  positions  with  regard  to 


Fig.  X. 

each  other  will  always  be  the  same  wherever  either  of 
them  may  be.  Thus,  in  Fig.  60,  we  found  the  position 
of  the  eccentric,  when  the  crank  was  at  B,  to  be  at  V  C, 
which  is  125°  ahead  of  the  crank,  hence  having  found 


Fig.  P. 

any  eccentric  position  the  corresponding  crank  position 
will  be  125°  behind  it. 

We  may  now  consider  the  return  stroke,  the  crank 
being  at  D,  and  we  may  suppose  the  load  at  the  port  B, 
Fig.  62  (which  is  the  one  that  must  now  act  as  a  steam 
port),  to  require  to  be  f  inch.  To  find  tlie  position  of 


'trm 


46 


MODERN   STEAM    ENGINES. 


the  eccentric  when  the  crank  is  at  D,  we  mark  s  distant 
from  C  to  the  amount  of  the  lap  and  the  lead  (or 
If  inches,  the  lap  being  1  inch  and  the  lead  f  inch). 
From  *  we  draw  the  line  s  v,  and  a  line  from  v  to  C  is 
the  required  eccentric  position,  being  135°  ahead  of  the 
crank  as  marked,  and  the  valve  will  be  in  the  position 
shown  in  Fig.  V,  port  J  being  open  to  the  amount 
of  the  lead.  When  the  eccentric  has  moved  to  the  end 
B  of  its  stroke,  the  valve  will  obviously  be  at  the  end 
of  its  stroke,  as  in  Fig.  B. 

The  next  event  will  be  for  the  valve  to  move  back  to 


valve  must  move  an  amount  equal  to  the  width  of  the 
port  or  distance  C  d  before  the  port  I  will  be  full  open 
for  the  exhaust,  hence  from  d  \ve  obtain  eccentric  posi- 
tion Z,  Fig.  62  and  valve  position  Fig.  Z. 

From  position  Z  the  eccentric  moves  to  the  end  D  of 
its  stroke,  the  valve  moving  to  the  position  in  Fig.  D. 
When  the  eccentric  arrives  at  11  the  valve  will  have 
moved  back  to  the  position  Fig.  Z  and  port  I  will  begin 
to  close  the  exhaust.  Then,  moving  the  width  of  the 
port  or  distance  from  d  to  C,  Fig.  62,  the  eccentric  will 
be  at  M'  or  mid-position,  the  valve  standing  in  its  mid- 


an  amount  equal  to  the  width  of  the  port  or  distance 
B  e,  Fig.  62,  giving  us  eccentric  position  y  and  the 
valve  position  shown  in  Fig.  Y.  The  next  event  is  the 
opening  of  port  5  to  the  exhaust,  the  valve  moving 
from  the  position  in  Fig.  Y  to  that  in  Fig.  M,  and  the 
eccentric  standing  in  mid-position  M,  Fig.  62.  The 


position,  Fig.  M,  and  closing  port  J  for  the  compression 
to  begin.  We  have  thus  found  the  eccentric  position 
for  all  the  events  of  the  stroke,  except  the  crank  posi- 
tion at  the  time  the  valve  is  ready  to  open  for  the  lead, 
and  this  we  find  as  follows  : 

With  the    valve    in    mid-position,  as  in    Fig.  M,  it 


UN  : 


DIAGRAMS  FOR  DESIGNING    VALVE  MOTIONS. 


47 


must    move   to    the   amount   of  its  steam   lap    l.etoiv    ii 
pen     to    the    trail,     hence    from    eccentric    niidpo.s; 

M'('.  in  Fig.  62,  measure  off,  on  the  left  of  C', 


V. 


>nt  from  C  to  ihe  .•iiiioiiiit  of  the  steam  lap.  From 
f  we  draw  the  vertical  line  <•  X.  giving  at  X  the  eccen- 
tric position  when  the  valve  is  in  the  position  Fig.  Y. 


B. 

To  find    the   corresponding  crank    position,  we   set   the 

' ipasses  to   the  radius  V  I),  and  from  X  mark  an  arc 

A'  and  draw  from  its  intersection  with  the  dotted  circle 


Fig.     Y. 

line  L'.  which  is  the  crank  position  when  the  eccentric 
is  at  X.  Fig.  62,  and  the  valve  in  the  position  shown  in 


F:,J.  M. 

Fig.  Y,    ready  to  open   for  the  lead  when   the  crank 
moves  towards  D. 


The   construction  of  Xeuner's  diagram  is  as  follows  : 
From  a   center  (,',   in   Fig.  0:i.  a  circle   11  I   D.  called  the 


travel  circle   is  struck,   its  circumference  representing 
the  path  of  the  center  of  the  crank  pin,  and  its  diame- 


Fig.  D. 

ter,  on  the  line  B  D,  representing  the  path  or  travel  of 
the  piston.     Now,  supposing  the  crank  pin  to  be  at  D 


'Qu^  . 
°"O. 


** 


ADMISSION 

BEGINS 


T*AVC.L  CI 

Fig.  63. 

and  to  require  to  revolve  in  the  direction  denoted  l»y 
the  arrow,  we  may  proceed  to  find  the  position  in  which 


48 


MODERN  STEAM    EXCflXES. 


to  mark  the  throw-line  of  the  eccentric.  If  the  valve 
just  covers  the  ports  and  has  neither  steam  lap  nor  lead, 
the  eccentric  throw-line  would  be  at  a  right  angle,  or 


ADMISSION 

BEGINS 


63. 


angle  of  90°,  to  the  line  from  C  to  D,  which  represents 
the  throw-line  of  the  crank  when  its  pin  is  at  D.  In 
proportion,  however,  as  the  valve  is  given  steam  lap 


\W 


supposed  to  have  such  an  amount  of  lap  and  lead  as 
would  require  the  eccentric  to  have  an  angular  advance 
of  36°  as  marked,  but  the  eccentric  throw-line  V  C 
(which  is  always  referred  to  as  representing  the  posi- 
tion of  the  eccentric)  is  shown  in  the  figure  to  stand 
behind  the  line  I  C  instead  of  ahead  of  it,  as  it  would 
require  to  do  if  the  crank  pin  was  at  D  and  ran  in  the 
direction  denoted  by  the  arrow. 

This  brings  us  to  a  feature  of  the  Zeunor  diagram 
that  renders  it  very  difficult  for  the  student  to  under- 
stand, and  which  must  be  mastered  before  he  can  have  a 
thoroughly  intelligent  conception  of  its  principles,  viz., 
that  it  is  essential  to  the  construction  of  the  diagram 
that  either  the  engine  be  imagined  to  run  in  the  oppo- 
site direction  to  what  it  would  actually  run  in,  or  else 
that  the  angular  advance  of  the  eccentric  be  given  in 
the  wrong  direction.  In  Fig.  64,  for  example,  the 
crank  pin  is  at  D  and  the  piston  at  the  head  end  of  the 
cylinder,  and  the  crank-revolution  being  in  the  diree- 
tion  denoted  by  the  arrow,  the  throw-line  of  the  eccen- 
tric would  be  at  W  (the  eccentric  being  marked  by  a 
full  line),  at  this  point  the  valve  would  be  in  the  posi- 
tion shown  in  the  figure,  its  edge  H  having  opened  the 
port  for  the  head  end  of  the  cylinder  to  the  amount  of 
the  valve  lead.  When,  therefore,  we  are  considering 
the  piston  and  valve  motions  for  the  crank  motion  from 
D  to  B,  we  are  considering  the  action  of  the  valve  upon 
the  port  for  the  head  end  of  the  cylinder  (except  as  re- 


and  lead  the  throw-line  of  the  eccentric  must  be  moved 
forward  in  the  direction  in  which  the  engine  is  to  run, 
and  the  line  I  C  is  merely  used  to  measure  the  amount 
to  which  in  any  given  case  the  eccentric  is  thus  moved, 
or,  in  other  words,  to  measure  the  angular  advance,  as 
it  is  called,  of  the  eccentric.  In  the  figure,  the  valve  is 


64. 


gards  the  compression  which  will  be  explained  here- 
after). The  construction  of  the  diagram,  however,  re- 
quires that  the  throw-line  of  the  eccentric,  instead  of 
being  marked  in  at  its  proper  position  in  advance  of 
the  line  I  C,  shall  be  marked  in  at  the  same  angle  from 
I,  but  on  the  right  oCJ  C,  as  shown  in  the  figure  by  the 


Dl.\f;i:.\M*  l-'oi:  DESIGNING    VALVE 


49 


nulia!  lino   V  C.     This,  lie   it  observed,  is   the  position 
U  would   occupy  if  the   crank    pin  \vcrc  ;it     B    and    the 
.   at    the  other  end  of  the  cylinder,   the 
of  crank  revolution  being  reversed. 

'I'd  efface  from  the  mind  the  reiiietnlirance  that  the 
:ii:e  \"  ('  of  the  eccentric  is  on  the  wrong  side  of 
the  line  I  < '.  and  therefore  in  an  assumed  or  false  po-i- 
tion,  the  crank  is  a-siimed  to  IK.'  on  the  opposite  dead 
center  to  what  it  actually  is.  and  the  engine  is  assumed 
to  run  in  the  contrary  direction  to  what  it  actually  docs. 
This  leads  to  further  complication  in  the  mind  because 
it  necessitates  (hat  it  l/e  asMimed  that  when  the  crank 
is  at  I>  it  is  the  port  at  the  head  end  that  is  acting  as  a 
steam  jiort,  whereas  it  is  the  port  at  the  crank  end  that 
is  actually  doing  .-<>.  l!ut  it  is  much  easier  to  associate 
the  mind  with  the  idea  that  the  throw-line  of  tin- 
trie  may  !«•  at  V  ( '.  or  In-hind  the  crank  instead  of  at 
\V  ('.  and  a!  i  ad  of  it,  because,  ill  this  case,  wo  may 
think  of  the  crank  as  running  i"  the  right  direction 
and  the  propel-  port  to  lie  acting  as  a  steam  port.  Thus, 
in  the  figure,  it  is  assumed  that  the  crank  is  at  D,  run- 
ning in  the  direction  of  the  arrow,  while  the  valve  is  in 
its  proper  po.-itioii  with  relation  to  the  crank.  During 
.ink  motion  from  D  to  B,  the  valve  edge  H  is, 
•  .re,  the  one  that  will  act  to  first  open  the  port  and 
admit  the  steam  and  then  close  it  and  effect  the  cut -off , 
while  the  edge  •  i>  the  one  that  will  reopen  the  port 
and  cause  the  exhaust,  and  edge  C  will  effect  the  coin- 
pres-ion  at  the  other  end  of  the  cylinder. 

llesuiuing  consideration  of  the  construction  of  the 
diagram,  in  Fig.  ('<:>.  the  position  of  the  eccentric  is,  for 
the  reasons  stated,  assumed  to  U-  behind  the  eccentric 
to  the  same  amount  (36°  in  the  example),  as  it  ought 
to  l>c  ahead  of  it. 

^  V  is  called  the  valve  circle,  and  its  center 
is  always  on  the  line  V  C.  Its  diameter  represents  one- 
half  the  amount  of  the  valve  travel.  Its  circumference 
always  pa.-ses  through  the  center  C  of  the  travel  circle 
B  I  D.  Tlio  valve  circle  for  the  other  piston  stroke  has 
:er  upon  the  line  C  v,  which  is  a  prolongation  of 
the  line  V  C. 

On  line  C  D  we  mark  a  point  d  distant  from  C  to  the 

amount  of  the  steam  lap  of  the  valve,  and  from  C  as  a 

center,  with  C  if  as  a.  radius  we  draw  the  outer  dotted 

ng  through  the  point  d.     This  is  called  the 


steam  lap  circle.  On  line  C  D,  distance  P  71  is  rqnid  to 
the  amount  of  exhaust  lap  of  the  valve,  and  point  .s  is 
distant  from  d  to  the  amount  of  the  valve  lead,  marked 
in  this  case  J  inch. 

Point  A  represents  the  position  of  the  crank  pin,  at 
the  time  when  the  valve  first  opened  the  port  to  admit 
steam,  and  as  A  C  represents  the  throw  line  of  the 
crank  at  this  time  .therefore,  angle  A  C  D  is  the  lead 
angle  of  the  crank.  Line  II  C  represents  the  center 
line  of  the  crank  at  the  time  when  the  steam  is  cut  off. 
Point  j  represents  the  position  of  the  crank  pin  when 
compression  begins  at  the  other  end  of  the  cylinder, 
and  in  represents  the  position  of  the  crank  pin  when 
the  exhaust  commences. 

The  return  stroke  is  similar,  in  fact  the  diagram  will 
apply  equally  well  for  both  strokes  if  simply  turned 
upside  down,  if,  as  we  have  thus  far  assumed,  the 
length  of  the  connecting  rod  be  assumed  to  be  infinite. 
It  will  be  observed  that  the  line  from  A  to  C,  showing 
the  position  of  the  crank  when  the  port  begins  to  open, 
is  drawn  through  the  intersection  of  the  lap  circle  with 
the  valve  circle  at  point  c,  and  also  that  the  point  of 
cut-off  H  is  obtained  from  a  line  drawn  from  the  center 
C,  and  passing  through  the  intersection  of  the  valve 
circle  with  the  steam  lap  circle. 

The  point  where  the  exhaust  commences  is  found  by 
drawing  aline  from  C  passing  through  the  intersection 
of  the  valve  circle  with  the  exhaust  lap  circle.  Now 
since  admission  commenced  when  the  crank  was  at  A, 
and  the  amount  of  steam  lap  is  equal  to  distance  C  d, 
therefore  the  valve  must,  when  the  crank  pin  is  at  A, 
have  moved  from  its  central  position  to  the  amount  of 
the  distance  from  C  to  c,  measured  along  the  line  C  A 
(the  point  c  being  at  the  intersection  of  the  valve  circle 
with  the  steam  lap  circle),  this  distance  being  equal  to 
C  d,  measured  along  the  line  C  D.  When  the  crank 
has  moved  from  A  to  D,  the  valve  has  moved  from  its 
central  position  and  opened  the  steam  port  to  the 
amount  of  the  lead,  or  the  distance  d  s.  Continuing  its 
motion,  the  crank  will  arrive  at  position  X,  and  to  find 
the  position  of  the  valve  we  draw  a  line  from  X  to  C, 
and  from  C  to  where  this  line  cuts  the  valve  circle  is 
the  amount  the  valve  has  moved  from  its  mid-position, 
being  shown  in  the  figure  by  the  distance,  or  radius, 
from  C  to  x.  To  find  the  amount  the  steam  port  would 


50 


MODERN  STEAM  ENGINES. 


be  open,  we  must  subtract  from  C  .T  the  amount  of  the 
steam  lap  or  radius  C  (/,  or  what  is  the  same  thing,  the 
amount  of  port  opening,  when  the  crank  pin  is  af  X, 
may  be  measured  on  the  line  X  C  from  x  (where  the 
line  X  C  cuts  the  valve  circle)  to  the  outside  lap  circle. 
When  the  crank  pin  has  arrived  at  V,  the  valve  will 
have  opened  to  its  fullest  extent,  hence  the  distance  be- 
tween the  travel  circle  and  the  valve  circle,  measured 
of  course  along  the  line  V  C,  represents  the  greatest 
amount  of  steam  port  opening  possible,  with  the 
amount  of  valve  lap  and  travel  given  in  this  example- 
When  the  crank  pin  reached  point  Y,  and  the  line  from 
Y  to  C  does  not  cut  the  valve  circle,  the  valve  is  in  its 
mid-position  over  the  ports,  and  both  ports  are  there- 


•** 


ADMISSION 

BEGINS 


Fig.   63. 

fore  closed.  Thus,  in  whatever  position  the  crank  pin 
may  be,  if  a  line  is  drawn  from  that  position  to  the 
center  C,  then,  from  the  point  where  it  cuts  the  valve 
circle  to  the  center  C  is  the  amount  the  valve  will  have 
moved  from  its  mid  or  central  position  over  the  steam 
ports.  Now  as  the  center  line  A  C  of  the  crank,  where 
the  steam  port  first  opens,  must  pass  through  the 
intersection  of  the  valve  circle  with  the  outside  lap 
circle,  as  at  c  in  the  figure,  and  as  this  center  line  must, 
at  the  point  H  where  steam  is  cut-off,  also  pass  throxigh 


the  intersection  of  the  valve  and  the  outside  lap  circle, 
it  follows  that  if  the  diameter  of  the  hip  circle  was  in- 
creased (giving  the  valve  more  lap),  or  diminished  (giv- 
ing the  valve  less  lap),  while  the  valve  circle  and  travel 
of  valve  remained  unaltered,  their  points  of  intersec- 
tion would  change,  hence  lines  C  A  and  C  H  (represent- 
ing respectively  the  crank  positions  at  the  points  of  ad- 
mission and  of  cut-off)  would  assume  different  posi- 
tions or  angles,  thus  locating  crank  points  A  and  H  in 
different  positions  and  changing  the  lead  angle  and  also 
the  crank  angle  at  the  point  or  moment  of  cut-off. 
Thus,  in  Fig.  65,  the  valve  travel  and  the  angular  ad- 
vance of  the  eccentric  remains  the  same  as  in  Fig.  (54. 
but  suppose  the  lap  circle  C  </,  Fig.  63.  be  increased  to  C 


Fig.  65. 

e,  Fig.  65,  and  to  locate  the  position  of  the  crank  pin 
when  the  valve  begins  to  open  the  port  for  the  admis- 
sion of  steam,  we  draw  a  line  from  the  center  C  through 
the  intersection  of  the  valve  circle  with  the  lap  circle  at 
c  and  locating  at  E  the  crank  pin  position  at  the  point 
of  admission  the  amount  of  lead  being  the  distance  e  S 
measured  along  the  line  C  D.  Similarly,  to  find  the 
point  at  which  the  cut-off  would  occur,  we  draw  a  line 
from  C,  passing  through  the  intersection  of  the  valve 
circle  with  the  lap  circle  as  at  n  in  the  figure,  and  we 
find  point  F  where  the  crank  pin  will  be  when  the 


DIAGRAMS  FOR  DESIGNING    VALVE  MUTlo.\*. 


51 


supply  will    be  cut   o!T  liy    ihe   valve.     Similarly, 

.•ad   cf  increasing  tin'  amount    of  strain    lap   we 

diminish   it,   as    denoted   by  the   inner  doited    circle  /. 

8  G,  cutting  tile  valve   circle  and    lap  circle/at  //. 

:  he  crank  pin   jxisitinti  \\l.i-n   the   port  is  first 

1  for  the  admission,  theamoi.  .,-    lead    he- 

.:  the  distance /'s.      The  line!'   K   pa-sing  through 

the   in  of  the  valve-   circle,  with   the    la: 

at  It.  gives  at    K    tin'   crank    pin    positional    the   point  of 

cut-off.       ll    is  seen,  -therefore,    thai    ceriaill    elclii' 

liie  valve  travel,  angular  advance  of  eccentric,  ami   the 

steam    lap    being   gi\vn,    the   amount    of   lead,    Creates! 

amount  of  port    opening  and   the  point   of  cni-olT  may 

md    on    tile    diagram.      <  >r,    COnVCN  8    poin! 

the  cut-oil  is   required   to  occur,  the   amount  of 


The  port  we  h&ve  bei-n  considering  is  port  b  in  Fig. 
66,  the  events  of  port  opening  and  cut-off  having  lieen 
governed  liy  the  edge  11  of  the  valve  while  the  exhaust 
'•rued  by  the  exhaust  edge  e.  But  while 
the  piston  is  performing  this  stroke,  there  will  have 
occurred  SOUP  -ion  in  the  other  port  (a)  in  the 

figure,  ii  being  obvious  that,  us  the  valve  is  traveling  in 
the  direction  of  the  arrow  d,  the  edge  c  of  the  valve 

will,  so  go  iias  closed  the    port   ,i,  shut  in  the  end 

the    cylinder   whatever   steam    has    not    been  ex 
hausted  from    the  previous  piston  stroke,  and   as   the 
piston   T    is  moving  in  the  direction  of    arrow/  the 
steam  thus  shut  in  will  be  compressed.     To  find  on  the 
.mi.  1'iir.   63,  at  what  point  this  compression  will 
(,.]•.  in  other  words,  to  find  in  what  position  the 


and  the  valve  travel  being  given,  the  necessary 
amounts  of  lap  and  angular  advance  of  eccentric  can 
be  found. 

l!'-:'erring  again  to  Fig.  63,  the  events  depending 
upon  the  exhaust  lap  may  be  similarly  located.  In  the 
figure,  the  imier  dotted  circle  p  represents  the  exhaust 
lap  circle,  and  a  line  drawn  from  center  C  and  through 
the  intersection  of  the  exhaust  lap  circle  with  the  oppo- 
Ive  circle  "\V  (this  point  of  intersection  being  at 
R  in  Fig.  63)  locates  the  crank  pin  position  when  the 
exhaust  begins  for  the  return  stroke. 


66. 


crank  pin  will  be  when  [the  edge  c,  Fig.  66,  of  the 
valve  closes  the  port  a  to  the  exhaust),  we  draw  from 
C,  Fig.  63,  a  line,  passing  through  the  point  where  the 
valve  circle  and  the  exhaust  lap  circle  cross  or  intersect, 
and  where  this  line  meets  the  travel  circle,  which  is  at 
j  in  the  figure,  is  the  position  of  the  crank  when  the 
compression  begins.  It  is  obvious  that  if  the  %-alve  had 
no  exhaust  lap,  the  exhaust  of  one  port,  as  b  in  Fig.  67, 
would  open  at  the  same  instant  that  the  compression 
would  begin  at  the  other,  as  a  in  the  figure,  and  that  if 
we  add  exhaust  lap  as  denoted  by  the  dotted  arc  in  the 


52 


MODERN   STEAM    ENGINES. 


figure  (the  valve  traveling  as  denoted  by  the  arrow),  we 
delay  the  exhaust  of  port  b  and  hasten  the  compression 
of  port  a. 


Fig.    67. 

Let  it  be  required  to  find  the  angular  advance  of  the 
eccentric,  the  points   of   admission,   of   cut-off  and    of 


travel  4  inches,  the  width  of  steam  port  being  1  inch. 
From  the  center  C,  Fig.  68,  we  draw  the  outer  or  travel 
circle  whose  diameter  is  4  inches  (equal  to  the  valve, 
travel).  Then  draw  the  line  B  D,  passing  through  the 
center  C,  and  the  line  C  I  at  a  right  angle  to  B  D. 
From  C  set  off  on  the  line  C  D  the  point  p,  equal  to  tl:<> 
given  amount  (§)  of  exhaust  lap,  and  draw  the  exhaust 
lap  circle.  From  C  also  set  off  the  distance  C  d  equal 
to  the  given  amount  of  steam  lap  (f  inch)  and  draw 
the  steam  lap  circle.  From  d  set  off  the  amount  of 
valve  lead  on  line  C  D  at  s.  Now,  from  C  and  .«  re- 
spectively, and  with  a  radius  in  each  case  of  one-half 
the  length  of  C  D  (or  one-half  the  radius  of  the  travel 
circle)  draw  the  two  dotted  arcs  at  c.  From  the  center 


Fig.  68. 


exhaust,  the  valve  having  £  inch  of  steam  lap,  f  inch 
exhaust  lap,  the  valve  lead  being  £  inch  and  the  valve 


C  draw  a  line  V,  passing  through  the  point  c  where  the 
dotted  arcs  intersect   and  prolong  this  line  across  the 


roi!    DESIONIMQ    VALVE  M<>Tlo\s. 


53 


tr.'i'.  •  to     7-.     Tliis  line    V    ('    i-    is    the  throw- 

hue  df   the  -  for    tin'   stroke   when 

tin-  piston  travels  fnnu  I)  to  1'.,  and  C  B  tor  the  stroke 

wlicn  tin-  piston  travels  from  1!  to  1).  Tin-  angular  ad- 
vance ^r  tl»'  eccentric  is  tin-  alible  V  ( '  I.  or.  us 
mar  From  jKiint  e,  on  the  line  ('  V.  \ve  draw 

valve  circle  having   a   iliaineter  of   ('  \'.  or  one-half 

of  the  travel  circle  I:  I).     For  the  other  stroke  we 

draw  a  similar  circle;   having  its  center  on   the   line  C  v. 

be  position  of   the   crank  when  the  port 

•••  the  admission  of  -  draw  a   line   from 

('   through   the    intersection  at    //  of  the   steam    lap  and 

valve  ciivles.  and  this  line'  prolonged  trives  at    A  the 

•  •  crank  pin  when  the'  port   begins  to  < 

11  (it    heine;    home    in   mind   that    the 
•rcle    represents   the    path   of   revolution   of  the 
crank  pin). 

To  find  the  position  of  the  crank  when  steam  is  cut 
oil.  draw  a  line  from  ('  passing  through  the  point  e  of 
intersection  of  the  valve  and  steam  lap  circles,  this  line 
jtiviiiLT  at  II  the  crank  position  at  the  time  the  valve 

8  port  and  cuts  oil  the  steam  supply. 

Similarly  with  regard   to  the  exhaust,  a  line  from  (' 

• -1.1th    the  intersection  of  the  valve  and  exhaust 

lap   circles,    itives    at  j  the    position   of  the  crank    pin 

when    the    exhaust  closes  nl   tin1   other   fin!  '//'  flu'  <•////;/'///-. 

hence    the  point  at  which  compression   liejjins.  at 

*;.v     To  (ind  the  crank  pin  position  when 

the    exhaust    Kevins,    we   draw,    from    C,  a  line   passing 

through  the  point  of  intersection  f  of  the  exhaust  lap 

circle  and   the'  oilier  valve  circle  (C   '•)  jjivinjt  at  m  the 

.ired   crank,   or  crank  pin.  position.      Now  suppose 

•ial  to  the  width  of  port,  in  this  . 

1  iii'  ..(I  from  the  steam  lap  circle  on  the  line 

C  T>.  giving  the  j>oint  VT  (distant  1  inch  from  <7)  then  a 

•  '    drawn    through  W.  and    from    Cos  a  center,  is 

,-dtho  port  circle.     The  distance  between  this  port 

circle  and  the  steam  lap  circle  is  the  distance  the  valve 

must  travel  after  the  admission  of  steam  before  it  leaves 

port  full  open.     Hence  when  the  crank  lias  reached 

T.    where  the   center   line   C   T  of    the   crank   pa 

through  the   intersection  of   the  port  circle  with  the 

valve  circle,  the  valve  lias  moved  the  distance  C  x  from 

on  over  the  ports,    and  if  from  this   we 

deduct  the  amount  of  the  valve  steam  lap,  or  radius 


('  '/.  we  obtain  the  amount    the   port  is   open  when   tho 
crank  is  at  T.  this  amount   lioimt  the   radius  '/  \V  OH 
line  (      I),  or  what  ia    tin;    same    tiling,  tin!   distance   /<  j- 
on  the  line  C  T. 

Mien,  that  since  the  steam  port  is  full 
open  when  the  crank  is  at  T,  the  edge  of  the  valve 
travels,  in  this  case,  over  the  bridge  between  the  steam 
and  exhaust  port  while  the  valve  is  moving  from  T  to 
V.  the  valve  liein^at  the  end  of  its  travel  when  the 
.  is  a!  V.  The  amount  of  the  over-travel  of  tho 
valve  is  obviously  represented  by  the  radius  X  T.  or  the 
distance  between  the  port,  circle  and  the  travel  circle, 
being,  in  this  case,  j  inch.  It  will  be  noted  that  in  the 
case  we  are  investigating,  the  steam  lap  is  j  inch  and 
the  port  1  inch,  and  the  valve  travel  being  4  indies  is 
more  than  twice  the  width  of  port  and  the  amount  of 
steam  lap,  and  hence  the  over-travel.  If  the  amount 
of  valve  travel  had  been  math'  twice  the  amount  ob- 
tained by  adding  the  width  of  the  steam  port  to  the 
amount  of  steam  lap,  the  travel  circle  would  also  have 


Fiy.   69. 

served  for  the  port  circle.  But  suppose,  on  the  other 
hand,  that  the  width  of  steam  port  had  been  1|  inches 
instead  of  1  inch,  and  then  the  dotted  arc  outside  or 
beyond  V  would  represent  tho  port  circle,  and  when  the 
valve  was  at  the  end  of  its  travel  at  V,  the  edge  of  tho 
valve  would  be  distant  from  tho  edge  of  the  port  to 
the  amount  the  dotted  arc  is  distant  from  V. 

Fig.  09  represents  the  case  in  which  the  port  circle  is 
at  W — the  port  width  being  an  inch — and  the  edge  H 
of  the  valve  travels  past  the  edge  y  of  port  I,  while 
Fig.  70  represents  the  case  in  which  the  port  circle  is 
at  the  dotted  arc  beyond  V  and  the  valve  sdge  H  does 
not  leave  port  I  full  open. 

In  Fig.  C3  and  G8,  we  have  taken  the  valve  and 
crank  positions  for  one  piston  stroke  only,  and  if  the 


or  h 

[TJ'NIVERSITY, 

CALIF 


54 


MODERN  STEAM  ENGINES. 


length  of  the  connecting  rod  be  left  out  of  considera- 
tion, we  may  invert  the  diagram  and  it  will  serve  for 
the  return  piston  stroke,  the  various  events  occurring  at 
the  same  points  in  the  crank  path,  although  not  for  the 


Fig.   70. 

points  of  the  piston  movement.  If  instead  of  a  con- 
necting  rod  a  slotted  crosshead  c,  Fig.  71,  be  employed, 
the  crank  pin  having  journal  bearing  in  a  sliding  block 
fitting  into  the  slot  of  the  crosshead  and  obviously 
passing  once  up  and  once  down  the  slot  at  each  revo- 
lution, then  the  crank  positions  and  the  piston  positions 
would  correspond,  and  the  events  of  cut-off,  exhaust, 


throughout  the  whole  piston  stroke  from  D  to  B,  the 
piston  being  at  its  second,  third  or  fourth  inch  of  move- 
ment from  D,  the  crank  pin  will  be  at  the  correspond- 

V          _ 

~  JI 


VII 


Fig.   72. 

ing  points  I,  II,  III  and  IV  respectively.     When  the 
piston  starts  from  B,  and  the  crank  (moving  in  the  direc- 


'- 

'    i     i       l 

li       i 

l        1       i 

Eg 

— 

i    i     i       i 

-=-r-  ^=-  =£=*  

EB 

— 

: 

- 

. 

: 

ii     i 

f 

1  i  i     i 

': 

L.J        L__J 

1 

.1 

3 

Pig.   71. 


compression,  etc.,  will  occur  at  equal  points  in  both 
piston  strokes.  Fig.  71  also  shows  the  valve  rod  F  to 
be  operated  by  a  slotted  crosshead  G,  which  is  done  so 
that  the  varying  angle  of  the  valve  rod  may  not  distort 
the  valve  motion  when  considered  with  relation  to  the 
piston  motion. 

Referring  to  Fig.  72,  for  example,  the  circle  rep- 
resents the  path  of  the  crank  pin  and  the  line  B  D  a 
piston  stroke  of  8  inches.  Now  suppose  the  crank  pin 
to  start  from  D  and  travel  in  the  direction  of  arrow  A. 
and  when  the  piston  had  moved  its  first  inch  as  denoted 
by  the  numeral  1,  the  crank  pin  will  stand  at  the  posi- 
tion I  on  the  upper  half  of  the  crank  circle  similarly 


tion  of  the  arrow  c)  travels  over  the  lower  half  of  the 
circle,  it  will  be  at  I  when  the  piston  has  moved  its  first 
inch,  at  II  when  the  piston  has  moved  its  second  inch, 
and  so  on.  Suppose,  then,  that  one  steam  port  is  full 
open  when  the  crank  is  at  position  II  on  the  upper  half 
of  the  circle,  and  the  other  steam  port  will  be  full  open 
when  the  crank  is  at  position  II  on  the  lower  half  of 
the  circle,  these  two  crank  positions  being  diametrally 
opposite.  Again,  if  the  steam  was  cut  off  when  the 
crank  was  at  position  VII  on  the  upper  half  of  the 
circle,  it  would,  on  the  return  piston  stroke,  be  cut  off 
at  point  VII  on  the  lower  half  of  the  crank  circle. 
The  same  rule  would  apply  to  the  exhaust  and  the  com- 


Dl .\<;n. \.\is  FOR  Jj/-:sn;\JXi;    VALVE  .i/o>77o.vx. 


55 


pression  for  the  two  strokes  which  would  also  oo-ur  at 

;  "Hiding  points  in  the  piston  ami  crank  movements. 

Tin-  eccentric  ro«l,  however,  is  so  long  in   proportion 

valve  travel    that    its    influence    on    the    valve 

motion  is  usually  too  small  to  be  of  practical  importance, 


end  of  the  connecting  rod  when  the  piston  is  at  N. 
Then  from  the  point  1'  we  mark  the  arc  X  J,  giving 
at  J  the  position  of  the  crank  when  the  piston  is  at  N 
and  the  cut-oil  for  that  stroke  takes  place.  Similarly 
for  the  other  stroke,  we  rest  the  compasses  at  R  and 


K 


C 

— •— 


Fig.   73. 


in  many  diagrams  for  plotting  out  valve  motions, 
its  length  is  taken  as  infinite  or  as  if  it  were  actuated  by 
ed  crosshead.  instead  of  by  an  eccentric.     The  in- 
fluence of  th(!  connecting  rod   in  varying  the  points  of 
cut-off,  exhaust,  etc..  on  one  stroke  as  compared  with  the 


mark  at  K  the  position  of  the  crosshead  and  of  the 
connecting  rod.  Then  from  K  we  mark  the  arc  R  H, 
giving  at  H  the  position  of  the  crank  when  the  piston 
is  at  R.  To  show  the  variations  in  the  two  crank  posi- 
tions, we  may  draw  the  dotted  line  S,  passing  through 


1 

,  1 

1     - 
j 

N            F 

V 

R 

^H      ' 

\ 

\    N^    / 

\ 

\   i   ^j/ 

\ 

\1    A 

V 

\  \  / 

X. 

Fig.  74. 


other,  may  be  shown  as  follows:  Suppose  that  in  Fig. 
73,  the  valve  motion  is  designed  to  cut  off  the  steam  at 
N  and  R,  these  being  equal  points  in  the  piston  strokes, 
the  length  of  the  connecting  rod  being  twice  the  length 
of  the  piston  stroke,  or  from  0  to  D,  and  to  find  the  posi- 
tions of  the  crank  at  the  points  of  cut-off,  we  set  a  pair 
of  conipa-ses  to  the  radius  C  D,  and  resting  one  point 
at  N.  we  find  at  point  P  the  position  of  the  crosshead 


the  center  of  the  circle,  and  it  Is  seen  that  the  cut-off  is 
later  during  the  stroke  in  which  the  piston  is  moving 
towards  the  crank. 

Now  suppose  the  valve  gear  is  designed  to  cut  off 
and  exhaust  the  steam  at  equal  points  in  the  crank  path, 
and  we  may  find  the  corresponding  piston  positions  oy 
the  construction  shown  in  Fig.  74,  the  length  of  the 
connecting  rod  being  twice  that  of  the  piston  stroke. 


56 


MODERN   STEAM    ENGINES. 


Continuing  the  construction,  we  set  the  compasses  to 
,  twice  the  radius  B  D,  which  will  represent  the  length 
'  of  the  connecting  rod,  and  (H  being  the  position 
of  crank  pin  at  the  point  of  cut-off),  we  set  the  com- 
passes at  II  and  mark  at  K  the  position  of  that  end 
of  the  connecting  rod.  Then  from  K  we  mark  the  arc 
II  R,  giving  at  R  the  piston  position.  Similarly  from 
J  we  get  the  piston  position  N.  The  difference  in  the 
two  piston  positions  may  be  found  by  measuring  from 
B  to  R  and  from  D  to  N.  For  the  piston  positions  at 


the  exhaust  of  the  return  stroke  we  get,  from  crank  posi- 
tion E,  the  other  end  of  the  connecting  rod  at  A,  and 
from  A  we  get  arc  E  F,  giving  at  F  the  piston  position 
when  the  exhaust  begins.  The  difference  in  the  points 
of  exhaust  being  seen  by  comparing  the  distance  B  V 
with  F  D. 

Referring  again  to  Fig.  68,  and  to  the  crank  position 
II.  the  length  of  the  connecting  rod  being  taken  as  two 
and  one  half  times  that  of  the  piston  stroke,  the  corres- 
ponding piston  position  is  shown  at  R.  On  the  return 


Fig.  68. 


the  respective  points  of  cut-off,  we  rest  the  compasses 
at  S,  the  crank  position  when  the  exhaust  is  to  begin, 
and  mark  at  T  the  position  of  the  crosshead  end  of  the 
connecting  rod  when  the  crank  pin  is  at  S.  From  T 
we  mark  with  the  compasses  the  arc  S  V,  giving  at  V 
the  piston  position  at  the  time  the  exhaust  opens.  For 


stroke,  the  crank  being  at  G,  diametrally  opposite  to  H, 
the  piston  would  be  at  P,  or  distance  P  D  from  the  end 
of  the  cylinder.  To  harmonize  the  points  of  cut-off 
with  the  piston  motion,  mark  r,  distant  from  D  to  the 
same  amount  that  R  is  distant  from  B,  and  by  means 
of  the  arc  r  g,  obtained  from  the  length  of  the  connect- 


/;/.!'//.'. l.l/.v  rolt  DESIGNING    VALVE  MOTIONS, 


5", 


mil.  we  find   (lie   i essary    crank    ;  at  .</. 

In  order  tn  enable  llu-  \a!\e  to  i-iit  iitT  stc:i;n  with  the 
crank  pin  at  v  and  ''"•  I':--''1"  at  ''•  corresponding  with 
the  piston  position  \\.  the  valve  must  lie  given 

MI  lap  for  the  port  nearest  to  the  crank — this  hein^ 
admitting  steam  while   the   crank    is  traveling 

i;iirli  the  half-revolution   1!  (I  I) — ami  in  order  to 
termine  ;  r  amount  of  steam  lap.  all  we  ha\e  to 

do  is  to  draw  a  new  steam  lap  circle  "  that  will  cut 
the  center  line  of  the  crank  at  the  point  //  where  it  is 
intersected  liy  the  valve  circle.  Hen-,  then,  we  ! 

di/ed  tin-  points  of  cut-oil  by  means  of  varying  the 
the   valve,  the    lap   for   crank   jwsition   II 
and  its  corresponding  piston  position   1!  being  the  radius 
and  that    for  crank    position  <j  and    the  correspond- 
ing  pi.-ton  position  /•  beiiisr  the  radius  C  a.     It  is  ohvi- 

ihat  in  varying  the  steam  lap  to  equalize  the  cut-off, 
we  have   varied    the  point   of    admission,    and    to   lind 

point  we  draw  the  dotted  line  E  C,  passing  from  C 
through  the  point  of    intersection  of  the  steam  lap  circle 

:id   the   lower  valve  circle  and  giving  at  K  the  crank 

tion  when  the  port  ojiens  for  admission.      When  the 
crank   reached   I!  the  amount  6f  valve  lead  will  bo  the 
a,  whereas,  on   the  other  stroke   it  is  but  d  s. 
\<  that  the  equalisation  of  the  points  of  cut-off 
can  only  he  done  at  the  expense  of  unequal  lead.      Sim- 
ilarly, the  compression  and  exhaust  might   be  equalized 

mvmg  different  amounts  of  exhaust  lap  to  the  two 
lips  of  the  valve  but  then;  is  one  condition  inevitable, 
which  is.  that  if  the  compressions  are  equalized,  the  ex- 
hausts must  he  unequal,  or  vice  versa.  To  summar- 
ize, then,  it  has  been  shown  that  with  a  valve  having  a 
given  amount  of  travel,  laps  and  lead,  the  points  of  cut- 
off, of  admission,  of  release,  of  compression,  and  the 
necessary  amount  of  angular  advance  of  eccentric,  may 
be  found,  but  the  form  in  which  the  problem  generally 
presents  itself  is  as  follows:  The  points  of  cut-off  and 
of  release,  the  width  of  port  and  amount  of  valve  lead 
for  a  given  engine  having  been  determined  upon,  it  is 
required  to  find  the  necessary  steam  lap,  the  amount  of 
valve  travel,  the  angular  advance  of  the  eccentric,  the 
amount  of  exhaust  lap,  the  point  at  which  compression 
will  begin,  the  position  of  the  crank  at  admission,  and 
the  lead  angle. 

Suppose,   for  example,  an  engine  has  a  piston  stroke 


of  '_' I  inches,  and  ired    to  cut  off  at  20  inches, 

release  ;,t  •_>:',  \    inches,  the  lead  to   be  j  inch,    tin 

ports  being    1  I  inches   wide  and   the  connecting  rod   <', 

feet     long. 

Draw  the  horizontal  line  B  D,  Fig.  75,  representing 
the  piston  travel,  and  from  its  center  strike  a  circle, 
1!  II  l>.  lo  represent  the  path  of  the  crank  pin.  Sup- 
posing the  engine  to  run  in  the  direction  of  the  arrow. 
we  set  ,i|T.  on  line  I)  B,  tin;  point  R.  the  position  of  the 
piston  when  steam  is  to  be  cut  off  on  the  stroke  as  the 
piston  travels  from  T)  to  I!,  ami  as  the  length  of  D  B  is  3 
inches  (or  '_'  I  oni'-i-ighths  of  an  inch),  R  will  be  20 
eighths  from  I>.  Wit  then  set  off  M,  the  point  in  the 
piston  stroke  at  which  the  release  or  exhaust  is  to  begin. 
Now  as  the  length  of  D  B  is  on  a  scale  of  one-eighth 
of  the  piston  stroke,  we  set  a  pair  of  compasses  to  a 
radius  of  one-eighth  the  length  of  the  connecting  rod, 
which  Ix-ing  72  inches  gives  a  radius  of  9  inches  (72  -=- 
8  =  9).  With  the  compasses  thus  set,  mark  from  R 
and  M  (in  the  manner  already  described  with  reference 
to  Fig.  73)  the  arcs  R  and  TO.  giving  at  R  the  position 
of  the  crank  at  the  point  of  cut  off,  and  at  m  the  crank 
position  when  the  release  or  exhaust  begins. 

From  H  and  m  we  draw  lines  to  the  center  C,  repre- 
senting at  C  H  the  center  line  of  the  crank  when  the 
cut-off  occurs.  Draw  a  line  C  T  bisecting  the  angle 
II  C  D,  and  from  D  erect  a  perpendicular  line,  meeting 
line  C  T  at  X.  Then  carefully  measure  the  distance 
C  D,  and  also  the  distance  C  X,  and  divide  C  X  into 
C  D,  thus  obtaining  a  fraction,  because  C  X  is  greater 
than  C  D.  Substract  this  fraction  from  1,  and  divide 
th(>  width  of  the  steam  port,  minus  one-half  the  lead, 
by  the  remainder,  which  will  give  the  half  travel  of 
the  valve  and,  therefore,  the  radius  of  the  travel  circle. 

Thus  distance  C  D  =  1^  inches  and  C  X  is  3.4 
inches.  Dividing  1£  (or  1.5)  by  3.4  gives  .44  which 
substracted  from  1  leaves  .56. 

The  width  of  port  is  1^  and  the  valve  lead  is  \,  half 
of  the  latter  is  |  and  1^  less  |  is  1-J  or  1.125.  Divid- 
ing 1.125  by  .56  gives  2,  and  2  inches  is,  therefore,  the 
required  half  valve  travel.  Hence  a  circle,  E  I  F, 
struck  from  center  C,  with  a  radius  of  2  inches,  is  the 
travel  circle,  and  E  F  or  4  inches  is  the  full  travel 
of  the  valve. 

Now,  from  the  point  T  of  intersection  of  this  travel 


58 


MODERN  STEAM 


circle  with  the  line  C  X,  draw  a  perpendicular  line  T  t, 
and  set-off  on  C  D,  and  on  each  side  of  t,  a  distance 
equal  to  one-half  the  lead  or,  in  this  case,  ^  inch,  thus 
getting  points  d  and  s. 


line  of  the  eccentric  as  in  our  former  examples.  The 
angle  C  I  V  is  the  angular  advance  of  the  eccentric, 
being,  in  this  case,  about  30°  as  marked.  The  eccen- 
tric throw-line  V  C  v  and  the  travel  circle  E  F  being 


Fig.   75. 


Then  C  d  is  the  steam  lap  and  a  circle  struck  from  C 
as  a  center,  and  passing  through  d,  is  the  steam  lap 
circle.  Now  from  s  erect  the  line  s  V  at  a  right  angle 
to  line  B  D,  and  from  V,  where  this  line  cuts  the  travel 
circle,  draw  the  line  V  C  v,  which  represents  the  throw- 


obtained,  we  may  now  draw  in  the  valve  circles  and 
then,  as  has  been  explained  with  reference  to  former 
figures,  the  line  A  C  may  be  drawn,  showing  at  A  the 
crank  pin  position  at  the  time  of  admission. 

To  find  the  necessary  amount  of  exhaust  lap  we  draw 


DIAGRAMS   FOR    DESIGNING     VALVE   MOTIONS 


59 


from  point  -ink  position  when  the  exhaust  is  to 

i    line    to  C,  and   where  this   line   cuts    the   travel 

•  p,    is  the   radius  of   tin'  exhaust   l.-ip   circle. 

may  therefore  lie  drawn,  from  C  01  I  '-enter,  with 

The  I  ravel,  angular  advance,  and  the  valve 

have  1 11   found    for   o  and    they  must 

In-  the  same  tor  both  strokes.     Tin-  steam  lap  ai 

haust  lap  of   the  valve  for  one  stroke  have  al-o   1  ieen  tie- 

tiTiiiim-il.  and  these  laps  may  lie  made  the  sa 

id  of    the  valve  of  they  may    lie  varied.       If   it  is 

•,;ned    to  vary  them,  it  must    lie  remembered    that 

-MOII   for  one  stroke  depends  upon    the  point 

ch    exhaust    begin-   i  :i    the   other   stroke   (as    was 

shown   in    Ki.i;.    'ii!   and    I'M),    hence  the   point    al    which 

compression  Kevins,  caiinoi  lie  found  until   the    point  of 

release  is  known.       If  the    laps   arc   to    l,e   ei|iial    at    each 

end  of  the  valve,   then   ('  /.  drawn  through  the  intev- 

the  exhaust    lap  circle  and    tin-  valve  circ 
would  give  /   as  the  point  at    which    compression  begins 
mi  the  return  stroke,   and   a  point  exactly  opposite  to  /, 
as  point  /.  would  lie  the  point  of  compression  (or  closure 

aust)  at  tl nd  P>  of  tin-  cylinder.     The  arc  »  N 

is  introduc-ei]  to    illustrate   the   fact  that    if  it    had    1 n 

lined   to  let   the  point   of  release  be  at    the  23rd 
inch  of  piston  stroke,  instead  of  at  23^  inches,  then  the 
vould.  al   the  time  the  release  occurred,   lie  at  n  in 
an-l     it    would   be  almost  impossible,  to 
:iine   with  certainty  just  where  the   line  »  C  inter- 
ne   valve   circle,   this   point  of  intersection   being 
-ary  in  order  to  find    tlie  required  amount  of  ex- 
haust lap. 

This  defect  in  the  Zouner  diagram,  however,  may  be 

remedied  by  drawing  it  to  a  scale  a  certain  number  of 

greater  than  the  given  dimensions,  and  then  cor- 

:dingly    reducing  the  results  obtained  from   tho 

diagram. 

it  now  lie    required    to  construct  a  diagram   to 
ihically,  the  actual  and    relative  openings    of 
and  exhaust    ports,  and  also  the  travel  of  the 
\a\    edge  (of  that   end    of  the-   valve  that  is  admit- 
ting live  steam)  over   the   bridge  and    the  exhaust  port, 
the  dimensions  being  as  in  the  subjoined  table. 

The  travel,    steam    lap.  exhaust   la]>  and    lead  being 

given,  a  diagram,  similar  to  that,  given  in  Fig.  li.r  may 

-tructed  from  the  given  data,   showing  the  travel 


Hid  the  valve  travel,  and  containing  the  steam 
and  exhaust  lap  circles,  the  valve  circles,  the  angular 
advance  of  eccentric  and  the  lead,  these-  lines  being  re- 
pealed in  l-'ig.  7ii.  in  which  1!  I)  represents  the  valve 
travel).1)  inches*.  I!  1  1>  is  ihe  i  ravel  circle.  I)  />  the  ex- 
<'  d  the  si  earn  lap  circle,  d  s  the  lead 
(i  inch).  V  0  «  the  eccentric  throw-line,  and  VAC 
and  C  K  /•  the  valve  circles. 

Width  of  steam  port  1^.  in. 

«         •'   exhaust  port  -     2-£      " 

"  bridges      -  1£ 

'•          '•    steam  1  ip  - 

Exhaust  lap       -  ^ 

Travel  of  valve       -  -         -         -     5 
I'i-ton  stroke     -  24 

Length  of  connecting  rod  -    84 

These  dimensions  being  taken  from  a  "  Rogers"  Loco- 
motive. 

I'Yoin  center  C,  draw  above  B  Da  semi-circle  as 
W  \V.  a  distance  from  the  steam  lap  circle  equal  to  the 
width  of  port  (1^-  inches),  and  this  may  be  called  the 
steam  port  circle.  Then  from  center  C,  and  below  B  D, 
draw  another  semi-circle  E  E,  distant  from  the  exhaust 
lap  circle  also  equal  to  the  width  of  port;  this  may  be 
called  the  exhaust  port  circle.  From  C  as  a  center, 
draw  a  semi-circle  F  F,  having  a  radius  equal  to 
the  width  of  tho  bridge  less  the  amount  of  exhaust  lap; 
this  may  be  called  the  bridge  circle. 

Considering  B  D  to  represent  the  piston  stroke,  it 
must  be  divided  into  24  equal  parts  as  I,  II,  III,  IV, 
etc.  (the  stroke  being  24  inches),  each  of  which  will 
represent  an  inch  of  piston  travel;  and  arcs,  I  1,  II 
2.  Ill  3,  etc.  (obtained  with  the  compasses  set  to  repre- 
sent the  length  of  the  connecting  rod,  on  the  same  scale 
as  B  D  represents  the  length  of  the  piston  stroke),  will 
give  the  corresponding  crank  positions,  the  direction  of 
crank-revolution  obviously  being  as  denoted  by  the 
arrow. 

Having  found  the  crank  pin  positions  corresponding 
to  the  piston  positions,  we  may  draw  lines  1  C,  2  C, 
3  C,  etc..  representing  the  throw-lines  of  the  crank  for 
the  respective  positions.  Now,  suppose  the  crank  is, 
say,  at  Z,  traveling  to  the  dead  center  D,  and  begin- 
ning with  the  point  at  which  the  lead  opens,  we  may 
trace  out.  on  the  upper  half  of  the  diagram,  the  move- 
ment of  the  steam  edge  of  the  valve  (H,  Fig.  64)  and 


60 


MODERX   STI-'.AM    KXULXES. 


the  corresponding  steam  port  openings,  and  simulta- 
neously upon  the  lower  half  of  the  diagram,  the  move- 
ment of  the  exhaust  edge  [<•,  Fig.  64]  of  the  valve. 
Next  we  may  trace  out  the  movement  of  the  exhaust 


are  covered  by  the  valve,  hence  the  ports  are  closed  to 
both  the  steam  and  exhaust.  But  when  the  crank  has 
readied  the  point  Z,  this  point  being  found  by  a  line 
from  C,  intersecting  the  valve  and  exhaust  lap  circles, 


17 


18 


21 


edge  [e,  Fig.  64]  over  the  bridge  and  over  the  exhaust 
port. 

When  the  crank  stands  at  Y,  or  at  a  right  angle  to 
C  V,  the  valve  is  in  mid-travel  and  both  steam  ports 


the  valve  has  moved  from  its  central  position  to  an 
amount  equal  to  the  exhaust  lap,  thus,  opening  the 
exhaust  at  the  end  B  of  the  cylinder.  When  the  crank 
has  moved  to  A,  the  radial  line  from  crank  pin  A 


///.|'//M.I/N 


DES1GX1XQ    VALVE  J 


Cl 


through  the  intersection  of  the  valve  circle  with 

lap  <'ircle.  and  the   valve   has   traveled  from 

ion  to  an  amount  equal  to  the  steam  laj> 

('  ./,  and  the  steam  edge  of  the  valve  coincides  with  the 

•  f  the  ]>ort,  lu'nce  the  admiuum  of  steam  begins. 

\haust  edge  at    the  other  end  of   the  valve  I 
<:i)  has  also  traveled  an  equal  distance,  as  shown  at  C  e, 
and  the  exhaust  is  open  the  distance  ('  <.  as  denoted   l.y 

avy    line  u.      "\Vhen   the   crank   has   reached    the 

TV  the  steam  edge   (II.  Fig.   I',  I )  of  tllC  valvo 

nit.  on  line  r  T>.  from  tin-  steam   lap  circle  to  the 

•vtion  of  the    valve    circle,   or    distant   d  S  away 

from   the    edge  of  the   steam    port.   gh  ing  an   opening 

'/  S.  or  I  inch  as  lead.     The  exhaust  opening,  when  the 

ifl  at   I».  is  from  ilie  exhaust  lap  circle  to  the  valve 

or  the  length  of  the  heavy  line  from   C  to/ 

When  tin'  crank  pin   is  at   the    position  marked   1  on 

the  travel  circle,  and  the  piston  has  moved  to  1  on  the 

line  D  li.  the  steam  port  is  open  the  length  of  the  lieavy 

line  I!'  which  extends  from  the  lap  circle  to  the  valve 

circle,  while  the  exhaust  at   the  other  end  (measured  on 

the  line  1  (.'   prolonged    beyond  C)   would  be  from  the 

exhaust  lap  circle  to  the  circle  E,  or  an  amount  equal 

length  of  the  heavy  line  t>.  Proceeding  to  the 
second  inch  of  piston  movement,  marked  II,  and  the 
Corresponding  crank  position  marked  2,  the  amount  the 
valve  lias  moved  from  its  mid-position  over  the  ports 
is  the  radius  from  the  lap  circle  to  the  valve  circle,  but 
the  width  of  the  port  is  only  that  from  the  lap  circle  to 

>rt  circle  W,  hence  the  actual  amount  of  steam 

the  length  of  thickened  line  C',  which 

extends  from  the  steam    lap  circle   to  circle  "W,  and  it 

appears  that   the  steam  edge  of  the  valve  has  traveled 

d  the  port  edge  and  over  upon  the  bridge.  The 
amount  of  exhaust  opening  at  this  time  is  thickened 

running  from  the  exhaust  lap  circle  to  circle  E, 

the  port  is  still  full  open,  it  being  noted  that  the 
width  of  the  port,  now  acting  as  a  steam  port,  is  from 
the  lap  circle  "W,  while  the  width  of  the  other  port, 
now  acting  as  an  exhaust  port,  is  from  the  exhaust  lap 

10  circle  jJ.     Similarly,  at  the  third  inch  of  piston 
travel  and  the  corresponding  third  crank  position,  the 
is  opened  full,  the  thickened  line  G'  extend- 
in};  from  the,  steam  lap  circle  to  the  port  circle  W,  and 
lying  wholly  within  the  valve  circle. 


The  amount  the  steam  edge  of  the  valve  has  traveled 
over  the  bridge,  is  shown  l>y  the  dotted  line  n,  extend- 
ing from  the  port  circle  W  to  the  valve  circle.  The 
t  opening  is  still  full,  because  the  line  </  (a  pro- 
longation of  G'  C),  passes  from  the  exhaust  lap  circle 
to  the  circle  E  without  passing  outside  of  the  lower 
valve  circle.  The  steam  port,  it  will  be  seen,  keeps  full 
open  for  all  the  succeeding  crank  pin  positions  up  to 
the  liitli.  while  the  exhaust  port  remains  full  open  up  to 
the'  l!>th  crank  position,  which  corresponds,  of  course, 
to  the  I'.ith  inch  of  piston  stroke.  The  over-travel  of 
the  valve  increases  until  the  crank  is  between  the  Sth 
and  Hth  positions,  and  then  gradually  diminishes,  finally 
ceasing  just  after  the  10th  piston  and  crank  positions. 

In  Fig.  77,  the  valve  is  shown  at  the  extremity  of  iU 


'i<j.   77. 


travel,  or  in  the  position  it  would  occupy  when  the 
crank  pin  stood  at  V,  and  the  over-travel  is  shown  at  X. 
The  exhaust  edge  of  the  other  end  of  the  valve  would 
be  the  distance  C  v,  Fig.  76,  from  its  central  position, 
and  the  port  opening  being  from  C  to  circle  E,  the 
exhaust  edge  of  the  valve  travels  past  the  port  the  dis- 
tance from  v  to  the  exhaust  circle  E,  this  distance  being 
represented,  in  Fig.  77,  by/>.  Now  we  have  seen  that 
as  the  crank  proceeded  from  D  towards  V,  the  steam 
edge  of  the  valve  traveled  across  the  steam  port,  open- 
ing it  full,  and  finally  passed  upon  the  bridge,  and  at 
the  same  time  the  exhaust  edge  of  the  same  end  of  the 
valve  passed  over  the  exhaust  port  A,  as  represented  at 
a,  Fig.  77.  Thus,  in  Fig.  76,  considering  piston  and 
crank  positions  1,  the  steam  end  of  the  valve  was  then 
distance  C  h  from  its  central  position,  and  hence  the 
distance,  on  line  (,'  1.  between  the  heavy  dotted  bridge 
circle  F  and  the  valve  circle  or  distance  F  h,  is  the 
amount  (a.  Fig.  77)  that  the  exhaust  edge  projects  over 


G'J 


MODKRX  STI-:.\M  ENGINES. 


the  bridge  and  across  the  cylinder  exhaust  cavity. 
"With  the  crank  in  posttion  2,  this  distance  [«,  Fig.  77J 
would  be  from  i  to  the  bridge  circle  F,  measured  on 
the  radial  line  C  '2,  and  so  on  to  position  V  of  the 


tance  being  represented  in  Fig.  77  by  a.  It  is  obvious 
that  in  all  cases  in  which  the  width  of  opening  at  e, 
Fig.  77,  is  less  than  the  width  of  the  port  B,  the  width  e 
is  the  effective  one  and  is  the  one  that  must  be  consid- 


76. 


crank;  at  which  time  this  exhaust  edge,  corresponding 
to  edge  e  in  Fig.  64,  would  project  over  the  exhaust 
cavity  equal  to  the  distance  from  the  travel  circle  to  the 


bridge  circle  F,  or  distance  V  j  in  the  figure,  this  dis-     bridges  and  of  the  cylinder  exhaust  cavity  relatively  to 


ered.  Cases  are  not  uncommon  where,  in  increasing  the 
amount  of  lap  on  an  existing  valve,  this  point  is  over- 
looked, and  on  account  of  the  narrowness  of  the 


1)1. \ '//,'. I. l/x   l-'ui:    DESIGNING    VALVE   .l/o'/7o.vx. 


69 


the  amount  of  valve  travel,  the  exhau-t  is  cramped  ami 
partially  cut-oil.  This  cannot  occur  if  the  cylinder 

Mist  port  or  cavity  is  made  equal  to  the  radius  \"   /'. 
TI!.  plus  the  width  of  the  steam   port.  \vhicli  would 
guv.  in  the  exam  pie,  V/=  i|),  pins  width  of  steam  port 
=   I  L'J'J  inches,  as  the   required  widtli  of  cyl- 

inder exhaust  port,  and  as  the  dimensions  given,  in  stal- 
ing the  example,  were  •_'],  another  -^  has  Keen  allowed 
in  drawing  the  diagram,  so  as  to  prevent  the  exhaust 
from  being  cramped  at  ..  l-'ig.  77.  The  crank  position 
at  i:  if  cut-oil  and  of  compression  is.  of  course, 

found  li\  en  given   in    previous  examples,  and 

we  may  now  proceed  to  examine  the  port  openings. 
Suppose  the  pi-ton  has  reached  its  1  till  inch  of  motion, 
and  the  crank  stands  at  position  14,  then  the  amount  of 

•n  port  opening  will  he  denoted  by  that  part  of  the 
radial  line  C  14  that  is  thickened,  and  lies  between  the 
steam  lap  circle  -I  and  the  port  circle  "\V.  This  port 
opening  decreases  until  it  is  closed  on  the  dotted  line 
11  ('  where  the  cut  oil  is  located. 

Similarly  referring  airain  to  the  exhaust  of  the  other 
at  the   liith   inch  of  piston   movement,  correspond- 
ing to  crank  position  lit.  the  exhaust   port  is  full  open. 

-howti  by  the  full  line  from  C  to  the  circle  E. 
\Vlule.  however,  the  crank  is  moving  from  its  19th  to 

'-'nth  position,  the  port  begins  to  close  the  lower 
valve  circle,  cutting  the  circle  K  at  K,  so  that  when  the 
crank  has  reached  its  20th  position,  the  exhaust  has 
begun  to  close,  its  amount  of  opening  being  represented 


by  the  thickened  part  of  the  line  that  runs  from  20 
through  ("and  extends  until  it  meeta  the  lower  valve 
circle,  this  thickened  part  Ix-ing  from  the  exhaust  lap 
circle  to  the  lower  valve  circle.  At  the  time  that  the 
piston  has  arrived  at  the  point  of  cut-olT  II.  the  exhaust 
port  is  still  open  an  amount  equal  to  the  thick  line  from 
w  to  the  lap  circle,  this  line  being,  of  course,  a  continu- 
ation of  line  II  C.  When  crank  position  'l'.\  is  reached, 
where  the  radius  from  '.'3  to  C  passes  through  the  inter- 
in  of  the  valve  circle  with  the  exhaust  lap  circle, 
the  exhaust  on  the  crank  end  of  the  cylinder  closes 
and  compreeaion  begins  in  that  end  of  the  cylinder. 
When  the  crank  •  reaches  m — line  m  C  passing  through 
the  intersection  of  the  exhaust  lap  and  the  lower  valve 
circle— the  exhaust  port  at  the  head  end  of  the  cylin- 
der opens.  Meanwhile  compression  continues  from 
crank  position  23  until  tin;  crank  arrives  at  a  distance 
from  B  equal  to  A  I),  when  steam  is  admitted  at  the 
crank  end  port,  and  the  same  events  are  repeated  during 
the  next  piston  stroke. 

If  we  attempt  to  give  to  the  valve  sufficient  lap  to 
cut-off  the  steam  at  a  point  earlier  than  at  about  five- 
eighths  of  the  piston  stroke,  and  at  the  same  time  keep 
the  lead  equal,  the  points  of  cut-off,  of  release  and  of 
cushion  vary  so  much  on  one  stroke,  as  compared  to  the 
other,  as  to  render  it  necessary  to  adopt  a  different  form 
of  valve  mechanism  in  which  a  separate  cut-off  valve 
is  employed. 


/^ei    , 

ItTBTIVEB   -ITT; 
V      - 
\^C  . 


CHAPTER    III. 


LINK    MOTIONS    AND    REVERSING    GEARS. 


With  the  valve  mechanism  thus  far  described,  the 
engine  is  capable  of  running  in  one  direction  only,  and 
to  enable  it  to  run  in  either  direction,  the  link  motion  is 
employed. 

The  link  motion  also  enables  the  travel  of  the  valve 
to  be  diminished,  and  this  causes  the  steam  supply  to 
the  cylinder  to  be  cut  off  earlier  in  the  piston  stroke, 
thus  using  the  steam  more  expansively. 

STEPHENSON'S  OPEN  ROD  LINK  MOTION.. 

Fig.  78  represents  an  open  rod  Stephenson's  link 
motion,  of  the  class  used  in  direct  acting  locomotives, 
or  locomotives  in  which  no  rocking  shaft  is  used.  Two 
eccentrics  are  employed,  one  for  the  forward  and  Dne 
for  the  backward  motion  of  the  engine,  and  as  there 
is  no  rocking  shaft,  the  forward  eccentric  leads  the 
crank — or  in  other  words,  is  ahead  of  the  crank 
when  considered  with  relation  to  the  direction  of  crank 
revolution — while,  with  the  engine  running  in  this  direc- 
tion, the  backward  eccentric  follows  the  crank,  whereas, 
when  the  link  motion  is  placed  in  backward  gear,  and 
the  direction  of  crank-revolution  is  reversed,  then  the 
backward  eccentric  leads  and  the  forward  eccentric 
follows  the  crank,  as  will  be  seen  more  clearly  presently. 
When  the  eccentrics  are  so  arranged  that  with  the 

'  crank  on  the  dead  center,  shown  in  the  figure,  the  rods 
are  connected  as  shown,  the  link  motion  is  one  with 

1  64 


open  rods,  as  distinguished  from  one  with  crossed 
rods,  but,  nevertheless,  the  rods  will  be  crossed  when 
the  crank  is  on  the  other  dead  center,  as  will  be  seen 
presently.  , 

The  eccentric  rods  are  pivoted  to  the  link,  as  shown, 
and  the  link  is  pivoted  to  a  pin  upon  the  saddle  s, 
which  is  fast  upon  the  link.  The  link  hanger  is  pivoted 
to  the  saddle  pin  and  to  the  end  of  one  arm  of  the 
lifting  shaft.  On  another  arm  of  this  shaft  is  pivoted 
the  roach  rod,  which  is  also  pivoted  to  the  reversing 
lever.  The  sector  is  (in  connection  with  the  reversing 
lever  latch)  employed  to  hold  the  reversing  lever  in  the 
desired  position.  The  valve  spindle  moves  in  a  straight 
line  by  reason  of  passing  through  a  fixed  guide.  The 
link  motion  is  said  to  be  in  full  gear  when  the  link 
block  occupies  its  furthest  position  from  the  saddle-pin, 
because  it  is  in  this  position  that  the  link  block  gives 
the  most  or  full  travel  to  the  valve.  The  reversing  rod 
is  pivoted  at  its  lower  end  X,  and,  by  pulling  the  end  </ 
of  the  latch  rod  towards  handle  g,  the  latch  is  lifted 
out  of  the  notch  in  the  sector,  and  the  lever  may  be 
moved  to  the  left  until  the  latch  will  engage  with  one 
of  the  other  notches,  as  notch  3,  2,  1,  or  0,  which  is  the 
middle  notch.  On  releasing  rf,  the  spring  acting 
against  the  piece  e  will  force  the  latch  into  the  notch 
in  the  sector  and — the  latter  being  in  a  fixed  position — 
thus  lock  the  lever  in  place. 


I'  ij*.   7*  &  79  . 


FULL  GEAR 

FOR 
FORWARD  MOTION. 


CYLINDER  PORTS 


VALVE 
1     SPINDLE 


SLIDE  VALVE 


FULL  GEAR 

FOR 
BACKWARD  MOTION. 


CYLINDER  PORTS 

a 


SLIDE  VALVE 


65 


66 


MODERN  STEAM   ENGINES. 


Xow,  suppose  we  hook  up  the  lever  one  notch,  or, 
in  other  words,  move  it  so  that  the  latch  falls  into  the 
notch  marked  3,  the  lifting  shaft  and  link  hanger  will 
have  moved,  lifting  up  the  link  and  bringing  the 
center  of  the  saddle-pin  nearer  to  the  link  block,  and 
as  the  link  is  pivoted  upon  the  pin,  and  vibrates  upon 
it,  the  amount  of  motion,  imparted  to  the  link  block, 
will  be  reduced  as  will  the  valve  travel  also. 

If  we  move  the  lever  so  as  to  engage  its  latch  with 
the  notch  o  of  the  sector,  the  saddle-pin  will  be  brought 
level  with  the  link  block  and  the  valve  will  have  the 
least  amount  of  travel  and  the  earliest  point  of  cut-off 
that  the  link  motion  can  give;  this  position  is  called 


gear  for  forward  to  full  gear  for  backward  motion,  we 
have  brought  the  backward  eccentric  rod  in  line  with 
the  link  block,  and,  as  a  result,  the  engine  will  run 
backward,  or  in  the  direction  denoted  by  the  arrow  in 
Fig.  79. 

"We  may  find  the  positions  of  the  parts  of  a  link 
motion  with  sufficient  accuracy  for  all  practical  purposes 
by  the  following  construction: 

In  Fig.  82  n  represents  the  path  of  the  eccentric.  I 
the  line  of  engine  centers,  j,  /,'  the  center  line  of  the 
link,  k  k'  the  eccentric-rod  eyes,  B  the  crank  on  the 
dead  center,  w  the  center  of  the  cylinder  ports,  and  x 
the  center  line  of  the  valve. 


\l 


MID    GEAR. 


that  of  mid-gear,  the  positions  of  the  parts  being  shown 
in  Fig.  80.  Between  these  two  positions,  on  this  half 
of  the  sector,  the  lever,  and  therefore  the  link,  may  be 
hooked  up  in  as  many  positions  for  the  forward  gear 
as  there  are  notches  in  the  sector,  each  position  giving 
a  different  amount  of  valve  travel,  and,  therefore,  a 
different  point  of  cut-off  and  degree  of  expansion. 

Now,  suppose  we  move  the  reversing  lever  so  that 
its  latch  engages  notch  7  of  the  sector,  the  parts  will 
then  be  brought  to  the  positions  shown  in  Fig.  79, 
which  is  full  gear  for  the  backward  motion.  It  will  be 
observed  that  the  crank  and  the  eccentrics  stand  in  the 
same  position  in  all  three  of  the  figures,  and  that  in 
moving  the  link  we  have  moved  the  eccentric  straps 
around  upon  the  eccentrics,  and  in  moving  from  full 


80. 


"With  the  port  a  open  for  the  lead,  the  valve  must 
have  moved  from  its  mid-position  to  the  amount  of  the 
lap  and  lead,  or  distance  w  x,  hence  we  take  this  dis 
tance  and  from  the  center  C  of  the  crank-shaft,  mark 
an  arc  c,  and  then  with  the  length  of  the  eccentric-rod 
as  a  radius,  and  from  a  point  on  the  line  I,  mark  an  arc 
?•  r',  and  lines  e  and/  drawn  from  C  to  the  intersections 
of  arc  r  with  circle  «,  gives  the  positions  of  the  two 
eccentrics.  From  the  center  of  eccentric  /,  we  draw 
the  center-line  p  p'  of  the  link-slot,  and  the  arcs  />•  //' 
for  the  eccentric-rod  eyes.  This  is  practically  convri 
but  not  absolutely  so,  because  we  have  assumed  the 
distance  from  F  to  j>  to  be  the  same  as  the  distamv 
from  c  to  K,  added  to  that  from  K  to  ji,  whereas  the 
latter  is  the  greatest,  and  eccentric  e  would,  therefore* 


67 


68 


MODERN  STEAM  ENGINES. 


actually  stand  a  minute  distance  further  ahead  of  the 
crank.  The  amount  of  the  variation  will,  with  eccentric- 
rods  of  ordinary  length,  be  too  small  to  be  important. 

In  the  figure  the  length  of  the  rod  is  made  but  about 
three  times  the  valve  travel,  whereas  in  practice,  it 
would  be  about  ten  times,  hence,  the  construction  here 
given  is  practically  correct. 

In  considering  the  proportions  of  the  parts  of  a  link 
motion,  in  which  a  reversing  lever  is  to  be  moved  by 
hand  power,  it  is  evident  that  the  amount  the  link  must 
be  raised,  in  moving  it  from  full  forward  to  full  back- 
ward gear,  must  be  such  as  will  enable  the  operator  to 
move  the  reversing  lever  from  one  to  the  other  of  the 
end  notches  in  the  sector,  the  leverage  of  the  reversing 
lever  being  sufficient  to  enable  him  to  exert  power 
enough  to  raise  the  link.  The  longer  the  link  is,  how- 
ever, the  more  perfect  the  motion. 

As  the  upper  end  of  the  link  hanger  swings  upon  a 
fixed  pin  or  pivot,  it  is  obvious  that  the  link  swings  in 
an  arc  of  a  circle,  of  which  this  pin  is  a  center,  and, 
in  consequence,  the  eccentric-rod  eye  partakes  of  this 
motion  instead  of  moving  along  the  line  of  engine 
centers,  which  would  give  the  most  perfect  action ;  and 

,'3 


gives  very  nearly  the  same  port  openings  as  the  simple 
valve  gear,  the  difference  being  so  slight  as  to  have 
no  practical  importance,  as  may  be  seen  by  comparing 
the  full  line  diagram  Fig.  32,  with  the  diagram  Fig. 
128,  both  being  for  a  valve  motion  having  the  same 
dimensions,  but  the  former  is  with  the  eccentric  attach- 
ed direct  to  the  slide  spindle,  and  the  latter  from  the 
same  valve,  etc.,  with  the  link  gear  added. 

The  dimensions  below  are  those  used  throughout  the 
following  examples,  unless  otherwise  stated: 

Piston  stroke 24  in. 

Length    of  connecting-rod 72    " 

Travel  of  valve  in  full  gear 4-J  " 

Lead  of  valve  at  full  travel £  " 

Length  of  eccentric- rod 1  ?    " 

Length  of  link  from  center  to  center 
of  link-block  when  at  i's  extreme 

positions  in  the  link 13    " 

Length  of  link  hanger 14    " 

Width  of  steam  ports '. \\  " 

Lap  of  valve £ " 

In  Fig.  81,  the  parts  (represented  by  their  center  lines) 
are  shown  in  full  gear  for  the  forward  motion  in  the 
upper,  and  in  mid-gear  in  the  lower  part  of  the  figure. 
For  the  full  forward  gear  we  may  find  the  position 


it  follows  that  the  longer  the  link  hanger  is,  the  less 
curvature  its  arc  of  action  will  have,  and  its  line  of 
motion  will  be  more  nearly  parallel  with  the  line  of 
centers,  it  is  usually  made,  however,  but  little  longer 
than  the  link. 

The  lifting-shaft  arm  would  operate  most  perfectly  if 
it  were  as  long  as  the  eccentric-rods,  but  considerations 
of  space  and  handiness  usually  limit  it  to  about  one-half 
of  that  length. 

When  it  is  placed  in  full  gear,  a  link  gear,  or  motion. 


of  the  upper  end  of  the  link,  as  follows: 

AVe  take  the  length  of  the  eccentric-rod  (which  is 
measured  from  the  center  e  of  the  eccentric  strap  to  the 
center  k  of  the  eye  at  the  other  end  of  the  eccentric- 
rod),  and  add  to  it  the  distance  from  the  center  of  the 
eccentric-rod  eye,  to  the  center  of  the  link-slot  (or  dis- 
tance g,  in  Fig.  82).  aud  with  the  radius  so  obtained, 
rest  one  point  of  the  compasses  at  e,  and  mark  on  the 
line  of  centers  J,  an  arc,  which  will  give  at  e  the  position 
of  one  end  of  the  ,ink.  For  the  position  of  the  other 


69 


I 

\---^ 

vti 


?-  ^   ^ 
fc-M-*-  *— 


i* 


>=.'_^ 

«^ 


MODERN  STEAM  EX  GINKS. 


end  we  mark,  with  the  same  radius,  and  from  /  as  a 
center,  the  arc  from  p  to  c,  somewhere  on  which  we 
know  the  lower  end  of  the  link  will  come.  We  then 
take  the  length  of  the  link  (the  radius  from  p  to  p'  Fig. 
82,  being  taken  as  the  length  of  the  link)  and  from  c  as 
a  center,  mark  an  arc  p  thus  getting  the  position  of  both 
ends  of  the  link.  To  find  the  center  from  which  the 
center  line  of  the  link  slot  may  be  marked,  we  take  the 
same  radius  (the  length  of  the  eccentric  rod,  plus  the 
distance  g,  Fig.  82)  and  from  c  as  a  center,  mark  an  arc 
r  r,  and  from  p  as  a  center  mark  arc  Ji,  and  as  arcs  r  r 
and  h  intersect  at/  the  center  of  the  backward  eccen- 
tric, it  shows  that  from/  as  a  center  we  may  draw  in 
the  center  of  the  link  curve.  To  find  the  center  of  the 
link,  we  divide  the  length  cp,  of  the  link  in  equal  parts, 
and  find  its  center  at  m. 

With  the  length  of  the  link  hanger  as  a  radius,  and 
from  m  as  a  center,  we  mark  an  arc  v,  somewhere  on 
which  we  know  the  upper  end  of  the  link  hanger  will 
stand,  and  to  find  the  exact  position  we  proceed  as 
follows:  Take  the  length  of  the  eccentric-rod  (that  is 
radius  e  A-)  and  from  t,  mark  an  arc  which  will  fall  coin- 
cident with  c  on  the  line  of  centers  (this  arc  being  seen 
at  d.  in  the  lower  half  of  the  engraving),  and  then  from 
s,  and  with  the  same  radius,  we  mark  an  arc  a.  Mid- 
way between  a  and  c,  we  mark  a  line  I  at  a  right  angle 
to  the  line  of  centers. 

We  must  now  turn  to  the  lower  half  of  the  engra- 
ving, representing  the  link  motion  in  mid-gear,  and  find 
the  position  of  the  link  as  follows: 

With  the  radius  /  p,  (or  in  other  words  the  length  of 
the  eccentric-rod,  plus  radius  g,  Fig.  82),  and  from  e' 
as  a  center,  we  mark  an  arc  u,  somewhere  upon  which 
we  know  the  upper  end  of  the  link  will  be,  and  from  / 
we  mark  an  arc  u',  somewhere  upon  which  the  lower 
end  of  the  link  will  be.  Now,  as  the  middle  of  the  link 
(or,  in  other  words,  the  center  of  the  saddle-pin)  will 
be  on  the  line  of  centers,  we  mark,  from  the  line  of 
centers,  arcs  p  and  p',  giving  the  length  of  the  link. 

Then  (with  the  length  of  the  eccentric-rod  plus  the 
distance  g,  Fig.  82),  we  mark  from  the  upper  end  of 
the  link  an  arc  r',and  from  the  lower  end  an  arc  /(',  and 
where  these  two  arcs  intersect  on  the  line  of  centers  (at 
Z)  is  the  center  from  which  the  center  line  of  the  link 
may  be  drawn;  the  center  of  the  link,  or  of  the  saddle- 


pin,  being  on  the  line  of  centers  at  n'.  From  n'  we 
erect  a  perpendicular  line,  g  g,  to  the  line  of  centers  of 
the  link  in  full  gear  in  the  upper  half  of  the  engraving, 
thus  getting  at  n,  a  position  corresponding  to  ?/',  when 
the  link  is  in  mid-gear.  We  then  take  the  length  of  the 
link  hanger,  and  from  n  as  a  center,  mark  an  arc  w, 
and,  from  where  this  arc  cuts  the  line  I,  we  draw  a  hori- 
zontal line  ij  fj,  which  will  be  the  plane  on  which  the 
centerS  of  the  lifting-shaft  will  be;  hence  we  take  the 
length  of  the  lifting-shaft  arm,  and  mark  an  arc,  giving 
the  location  of  the  center  of  the  lifting-shaft  at  S. 
From  S  as  a  center,  with  the  radius  from  S  to  line  I,  we 
mark  an  arc  y  y,  and  where  this  cuts  arc  v  is  the  loca- 
tion for  the  upper  end  of  the  link  hanger  when  the  link 
is  in  full  forward  gear.  When  the  link  is  in  mid-gear 
the  link  hanger  will  stand,  one  end  on  the  line  of  cen- 
ters at  n,  and  the  other  at  the  intersection' of  arc  w  with 
line  q,  the  parts  occupying  the  positions  shown  in  Fig. 
79. 

It  may  now  be  shown  that  the  amount  of  lifting-shaft 
motion  necessary  to  lift  the  link  from  mid-position  to 
full  gear  for  the  backward  motion,  is  less  than  that  re- 
quired for  moving  the  link  from  mid-gear  to  full  for- 
ward gear.  Thus,  when  the  link  is  in  mid-gear,  its 
center  will  be  at  n',  as  has  already  been  shown;  hence 
from  n  with  a  radius  of  half  the  length  of  the  link, 
we  mark  an  arc  m'  somewhere  on  which  the  center  of 
the  link  will  be  when  in  full  gear  for  the  backward 
motion.  Then  from  e  as  a  center,  and  with  radius  e  c, 
we  mark  an  arc  u',  and  where  •«'  cuts  in'  is  the  position 
for  the  center  of  the  link  when  placed  in  full  gear  for 
the  backward  motion.  From  this  point,  therefore,  and 
with  the  length  of  the  link  as  a  radius,  we  mark  an  arc 
£  a,  and  where  this  cuts  arc  y  is  the  position  for  the 
upper  end  of  the  link  hanger  when  in  full  gear  for  the 
backward  motion,  and  if  we  measure  on  arc  y  from  a; 
to  w,  we  find  it  less  than  from  w  to  v,  and  this  obviously 
affects  the  positions  of  the  notches  in  the  sector.  We 
have  thus  found  the  positions  of  all  the  parts,  when  the 
crank  is  on  the  dead  center  B,  and  the  link  is  in  full 
gear,  and  also  when  it  is  in  mid-gear,  and  it  may  now 
be  pointed  out  that  in  moving  the  link  from  full  gear 
to  mid-gear,  we  have  increased  the  lead  of  the  valve. 
Thus  when  it  is  in  full  gear,  the  upper  center  of  the 
link  and,  therefore,  the  center  of  the  link-block,  is  on 


1J.\I\    MUT1U\.S. 


71 


p- 
r 


MODi-:r;\  STI-:AM 


>--  ^ 


L/.\/\~  .I 


73 


me  of  centers  at  <•.  ami  when  the  link  is  in  mid-.irear 

-    is   at   ;/.       l!y    means  of    the  vertical    line'///', 

\ve  have  transferred  [«•-  OH  tlie  lower  half  of  the 

•aving.    to  the    upper   ha  nd    it   is  clear  that. 

;r  center  of  the  link-Mock  is  always  coincident  with 
the  center  line  of  the  link  .-lot.  and  always  on  the  line 
of  centers  ''  /<  of  the  engine,  therefore  it  will,  in  moving 

link  from  full  to  mid-gear,  he  moved  from  <•  to  //. 
and  the  lead  will  lie  conv-poiidingly  increaseil. 

In  Fig.  *•'!.  the. parts  are  shown  in  position  for  full 
backward  gear,  the  construction  corresponding  to  that 

,dy  desrribed  and  being  as  follows;  radius/  A-'  is 
the  length  of  the  eccentric  ro<l.  to  which  we  add 
tance  ./.  in  Kiir.  si',  and  tret  radius/''/,  and  from  /'  as  a 
center,  mark  an  arc  <l.  With  the  same  radius  we  mark 
from  e  as  a  center,  arc  «'.  \Vitli  the  length  of  the  link 
and  from  <•  on  the  line  of  engine  renters,  we  mark  in 
at  '•'.  the  np[>er  end  of  the  link.  From  c',  with  radius 
we  mark  an  arc  r  >;  and  from  c,  with  the  same 
radius,  an  arc  h,  and  as  these  two  arcs  intersect  at 

•  >hows  that  e  is  the  renter  from  which  we  may 
draw  in  the  center  line  of  the  link  slot.  Then  by  divi 

_r  the  link  arc.  we  get  the  (•.•liter  ,,i.  of  the  link  and 
of  the  saddle-pin.  Thus  it  is  shown  that  when  the  link 
is  in  full  gear  for  either  the  forward  or  for  the  back 
ward  motion,  the  center  of  the  arc  of  the  link  slot,  is 
the  center  of  the  eccentric  that  follows  the  crank,  or  is 
behind  the'  crank,  in  the  path  of  crank  revolution. 

In  Kig.  st.  we  have  the  parts  in  the  positions  they 
occupy  when  the  link  is  in  mid-gear,  and  the  crank  on 
the  .lead  center  I),  and  it  is  -een  that  the  eccentric 
/'whose  rod  is  connected  to  the  lower  end  of  the  link 
now  leads  the  crank,  and  by  the  same  construction,  as 
in  the  previous  examples,  that,  the  center  line  of  the 
link,  may  l>c  drawn  from  the  renter  of  the  eccentric  (e 
in  this  case)  that  follows  the  crank,  which  is  found  to 

ihvays  the  case  when  the  link  is  in  full  gear  for 
either  the  forward,  or  backward  motion,  and  the  crank 

•n  the  dead  center.  The  amount  the  lead  of  the 
valve  will  be  increased  by  moving  the  link  from  full  to 
mid-gear,  is  shown  by  the  distance  on  the  line  of 
centers,  between  the  arc  c*c,  and  the  center-line  of  the 
link  slot.  By  inserting  a  pencil  in  the  center  of  the 
pin  connecting  the  eccentric  rod  to  the  link,  we  are  en- 
•41  bled  to  trace  the  path  of  motion  of  the  end  of  the 


eccentric  rod.  Thus  in  Fig.  85,  we  have  the  path  of 
motion  of  the  forward  eccentric,  when  in  full  forward 
gear,  and  for  the  stroke,  when  the  piston  is  moving 
from  the  crank  end.  to  the  head  end  ol  the  cylinder. 
The  line  /./.  corresponds  to  line  /./,  in  Figs.  83,  and  84. 
During  the  return  stroke',  the  rod  obviously  moves  in 
the  same  path,  but  the  events  occur  in  a  different  part 
of  the  figure,  as  ma  .  1m  seen  from  Fig.  86,  which  is  for 
the  return  stroke.  In  Fig.  ST.  we  have  the  path  of 
motion  of  the  pin,  that  connects  the  backward  eccentric 
to  the  link,  the  latter  being  in  full  backward  gear.  The 
events  for  the  stroke,  when  the  piston  is  moving  from 
tin-  crank  end.  to  the  head  end,  are  named  outside  the 
line  and  are  lettered  ,;.  b,  c,  etc.  For  the  other  stroke 
when  the  piston  is  moving  from  the  head  end  to  the 
crank  end.  the  events  are  denoted  by  letter  only,  thus  at 
I>.  the  crank  is  on  the  dead  center,  at  a';  the  port  is 
fully  opened  as  a  steam  port,  at  b';  the  valve  begins  to 
close  the  port;  at  c',  the  cut-off  occurs;  at  rf',  the  port 
opens  for  the  exhaust;  at  e'  the  port  is  full  open  for  the 
exhaust;  at/*,  the  port  begins  to  close  to  effect  the  cush- 
ion, and  at  g',  the  cushioning  begins,  lasting  of  course, 
until  the  valve  opens  for  the  lead.  In  Fig.  88,  we  have 
a  diagram  of  the  openings  etc.  of  the  ports,  the  full 
lines,  representing  the  full  backward  gear,  and  it  is  seen 
that  the  events  are  very  nearly  equalized,  there  being 
but  about  £  inch  difference  in  the  points  of  cut-off. 

In  Fig.  89,  we  have  the  path  of  motion  of  the  forward 
gear  eccentric-rod  eye,  when  the  link  is  hooked  up  to 
cut-off,  at  one  half,  in  the  forward  gear.  For  the  piston 
stroke  from  the  crank  end,  the  letters  outside  the  lines 
are  used,  thus,  at  B,  the  crank  was  on  the  dead  center 
at  the  crank  end;  at  a,  the  port  end  was  fully  opened, 
and  immediately  began  to  close.  At  C,  the  cut-off  oc- 
curred; at  (t,  the  port  opened  as  an  exhaust  port;  at  e,  the 
port  was  fully  opened  to  the  exhaust;  at /it  began  to  re- 
close,  and  at  g,  the  port  was  closed  to  the  exhaust  and 
the  cushioning  began.  For  the  other  stroke,  when  the 
piston  moved  from  the  head  end  to  the  crank  end,  and 
the  head  end  cylinder  port,  comes  under  consideration, 
D,  is  the  point  at  which  the  crank  was  on  the  dead 
center;  at  a',  the  port  was  fully  opened;  at  c',  cut-off  oc- 
curred, and  so  on,  the  events  for  this  stroke,  all  being 
marked  inside  the  lines  of  the  figure,  and  corresponding 
to  those  used  for  the  same  events  on  the  other  stroke, 


74 


M ODER  A"  STEAM  ENGINES. 


Fiys.   85  &  86. 


Paths  of  Motion  of  the  Eccentric-rod. 


a 
1* 


Line  of  Engine 
Centers. 


LINK  MOTIONS. 


75 


Fig.  88. 


Fig.  89. 


10 


76 


MODKRN  STEAM  KXGINES. 


except   that  to  eacli  letter  a  distinguishing  dot  or  mark 
is  added. 

The  line  /,  in  all  these  motion  curves,  corresponds  to 
line  7,  in  Figs.  81,  82,  and  83,  representing  the  link 
hanger  when  it  stands  at  a  right  angle  to  the  line  of 


represented  by  the  full  lines,  while  the  backward  gear  is 
marked  in  dotted  lines.  It  is  seen  that  the  points  of 
cut-off  are  exactly  equal,  for  both  gears  backward 
and  forward.  Thus,  considering  the  port  at  the  crank 
end  B,  (which  corresponds  with  B  on  the  motion  curves) 


90. 


centers,  and  the  link  is  in  mid-gear.  In  Fig.  90,  we 
have  the  motion  curve  of  the  backward  eccentric  rod> 
when  the  link  is  hooked  up  to  cut  off  at  half  stroke 


the  cut-off  for  both  gears,  occurs  at  12  inches  of  the 
stroke,  while  for  the  stroke  from  the  head  end  D,  of 
the  cylinder,  the  cut-off  occurs  at  the  14  th.  inch  of  the 


B 


14 


12 


8 


\ 


\ 


\ 


\ 


\ 


In  Fig.  91,  we  have  a  diagram  of  the  port  openings 
etc.,  for  the  cut-off  at  half  stroke,  on  the  stroke  from 
the  crank  end  to  the  head  end  of  the  cylinder,  (the 
designated  points  of  cut-off,  refer  to  this  stroke, 
throughout  all  the  examples,  letting  the  cut-off  for  the 
other  stroke  come  where  it  will).  The  forward  gear  is 


91. 

stroke.  The  points  of  release  and  cushion,  are 
almost  identical,  and  it  is  seen  that  the  events  are  as 
nearly  equalized,  as  possible.  The  lead,  however,  has 
been  increased  in  hooking  the  link  up  from  the  \  inch, 
it  was  with  the  link  in  full  gear  to  -fa,  at  end  B,  and  ).  I 
inch  at  end  D,  both  strokes  from  end  B,  and  both 


from  T).  thus  having  their  amounts  of  lead  equalized. 

li  will  U-  noted,  that  tin'  ports  open  wiilcst  on   both 

.  when  the  link  is  in  backward  gear,  and  that  the 

opens  wider  than  that  at  the  crank 

cnil,  whether  the  link  is  in  backward  or    forward    gear. 

This    latter   point   is    of    advantage.   beCM06    the    piston 

T  when  moving  from  I),  to  half  stroke,  than 


moving  (at  the  crank  pin  end),  away  from  the  line  of 
centers  during  one  part  of  the  stroke,  and  towards  the 
line  of  centers,  at  another  part. 

A  diagram  of  ihe  port  openings,  when  the  link  is 
hooked  up  to  cut  off  at  one  quarter  stroke,  is  given  in 
Fig.  !i'j.  the  full  lines  representing  the  forward,  and  the 
dotted  lines  the  backward  motion,  and  it  is  seen,  that 


Fig.  92. 

it  does  when  moving  from  B,  to  half  stroke,  and  there-    the  events  are  here,  also,  very  nearly  equalized,  or  occur 
fore  requires  a.  wider  port  opening,  in  order  to  admit 
more  readily. 


The  cause  of  the  faster  piston   motion,  has  already 


at  nearly  epual  points  on  both  the  backward  and  for- 
ward motions,  while  the  port  at  the  head  end  still  gets 
the  greater  opening. 


Fi<J.  93. 


explained,  with  reference  to  plotting  out  valve 
motions,  and  is  not  therefore  repeated  more  than  to 
recall  the  fact,  that  it  is  caused  by  the  connecting-  rod 


The  point  of  cut.off  for  the  head  end  D,  is  still  two 
inches  later,  on  account  of  the  connecting-rod  motion, 
as  before  explained-  "When  the  link  is  in  mid-gear,  the 


78 


MODERN  STHA  M   A-Y  G 1  .\  A'X 


motion  of  the  forward  eccentric-rod  eye  will   be  as  in 

ports.     But  this  alteration,  will  act  to  vary  the  points  of 

Fig.   03,    while    that  of     the    backward    rod    will    re- 

cut-off.    Suppose,  for  example,  that  instead  of  locating 

main  a  loop  as  before.     The  port  openings,  are  now  as  in 

the  line  1  I,  Figs.  81.  83,  and  84,  mid-way  between  the 

s 

~r-*. 

o 

N 

^ 

O 

4 
111 
-J 

\ 

,, 

•'* 

< 
1 

\ 

/ 

\ 

4 

1 

2 

t 

/ 

4 

/( 

i 

? 

, 

/ 

NS 

S 

1 

1 

f(/^ 
^ 

k. 

L 

^ 

<P 

/ 

C 

^ 

v 

//P* 

* 

> 

X 

\ 

/ 

X 

\ 

l-'ij.  1M. 


the  diagram,  Fig.  94.  The  valve  lead  is  here,  ^-|  inch 
and  the  ports  only  open  as  steam  ports  to  that  amount, 
the  valve  moving  to  close  the  steam  port,  as  soon  as  the 
crank  pin  leaves  the  dead  center  on  either  stroke. 


ICf 


\ 


\ 


\ 


\ 


12 


\ 


\\ 


N 


\ 


\ 


\ 


'Fig.  95. 

We  may  slightly  improve  the  admission,  by  putting 
the  point  of  suspension  of  the  link  hanger  forward, 
v.-hich  will  cause  the  ports  to  open  wider,  as  steam 


extremes  of  the  eccentric-rod  motion,  we  locate  it  mid- 
way between  the  extremes  of  the  link -block  travel 
(when  the  link  is  in  full  forward  gear)  the  lines  a,d.  Fig. 
83,  being  drawn  from  the  ends  of  link-block  travel,  iir 


\ 


\ 


/y 


\ 


x 


\ 


\ 


X 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


T) 


\ 


Fig.  96. 

stead  of  from  the  eccentric-rod  travel,  and  line  /  /.  1  < 
drawn  mid-way  between  them,  thus  throwing  the  center 
of  the     lifting-shaft    nearer  to    the    link.      The    effect 


/./.V/\-   MOTION'S. 


(UNIVERSITY, 
o« 


79 


in  full  gear,  is  to  ruu.se  the  point  of  cut-off  to  occur 
(on  the  stroke  from  the  crunk  rn<l  to  head  end),  £  inch, 
carliiT  for  the  backward,  than  for  the  forward  gear,  and 
on  the  other  stroke,  to  delay  the  point  of  cut-oil1,  making 
it  a  half  inch  later  than  in  Fii_r.  SS.  At  half  gear  the 
difference  is  more  marked,  as  may  he  seen  from  Fig.  '.!.">. 
which  on  comparison  with  Fig.  '.M.  shows  the  point  of 
rut-oft  for  the  backward  gear  ID  be  nearly  e(|iiali/ed, 
and  the  amount  of  port  opening  nearly  equalized,  Ijtit 
the  points  of  cut-off  for  tin-  backward  gear,  vary  from 
those  for  the  t'oruanl,  whereas  in  Fig.  !)1,  they  were 
identical.  At  i[iiarter  cut-oft  the  events  are  very  0681 
ly  equali/ed.  as  may  l>e  seen  from  Fig.  in;.  ]',ut,  there  is 
another  point  to  l.e  noted,  inasmuch  as  the  cut-oft  oc- 
curs at  the  Ttli.  inch,  whereas  in  Fig.  IK;,  it  occurs 
at  the  Sth.  inch,  on  the  stroke  from  I),  to  I>.  In  mid 
gear,  the  events  for  backward  and  forward  are  equal- 
ized, lull  the  cut-off  is  at  -I  and  .1  inches  respectively. 
.•is  seen  in  Fig.  H7.  whereas  it  was  in  Fig.  !»(i,  at  4  and 
.").l  inche>  iv>pectively.  Thus,  it  will  he  seen  that  the 

difference  caused  by  altering  the  posiiion  of  the  lifting- 
shaft  is  not  very  marked,  and  possesses  both  advantages 
and  disadvantages. 

SHIFTIXc;   THK   POSITION'  OF    THE  SADDLE-FIN. 

If,  instead  of  setting  the  saddle-pin  central  to  the 
width  of  the  link-slot  as  in  the  foregoing  examples,  we 
:  hark,  bringing  it  on  the  chord  of  the  arc  of  the 
link-slot,  we  shall  find  that  the  equalization  of  the 
events  is  impaired,  as  may  be  seen  on  a  comparison  of 
Fig.  in;,  with  Fig.  its,  the  latter  being  a  diagram  of  the 
port  openings,  with  the  saddle-pin  thus  set  back.  The 
point  of  link  hunger  suspension  is  the  same  for  both 
figure.-,  and  the  steam  supply  is  seen  to  still  be  better 
for  the  backward,  than  it  is  for  the  forward  gear 

Summarizing  these,  results,  wo  (ind  that  for  the  equal 
ixation  of  tin-  events  of  cut-off  etc.,  for  the  forward 
and  backward  motions,  it  is  preferable  to  suspend  the 
link  lianger.  as  in  Figs.  81,  and  84,  while  to  obtain  port 
.ings,  a-  nearly  equal  as  possible  for  the  backward 
and  forward  go.ars,  it  is  preferable  to  suspend  the  top  of 
the  link  hanger,  so  that  the  lines  n  <l,  Figs.  8.1,  and  84, 
are  drawn  to  represent  the  ends  of  travel,  of  the  link- 
Mock,  when  the  link  is  in  full  forward  gear,  the  line  / /, 


• 

Fig.  . si,  being  drawn  mid-way  between  the  lines  ad, 
and  the  lifting-shaft  center  being  set  from  line  I  I,  as 
described  in  Figs.  81,  S3,  and  84. 


EQUALIZIN'O  THE  LEAD. 


It  has  been  shown,  that  in    proportion   as   the  link  is 


\ 


\ 

\ 


/ 


'I 


X 


Fig.  97. 
moved  from   mid -gear,  to  or  towards  full  gear,  either 


t 

^ 

^ 

s, 

s-* 

^ 

.^ 

- 

^ 

\ 

y 

'/ 

\- 

y 

/ 

\ 

s 

/ 

x 

; 

x1 

^ 

V 

\ 

} 

/j 

^ 

\ 

I/ 

\ 

; 

/ 

\ 

t 

//' 

\ 

^ 

\ 

y 

/ 

/ 

N 

\ 

2 

f 

' 

\ 

\ 

S 

S 

Fig.  98. 
backwards   or   forwards,  the   valve 


lead    is   increased, 


80 


MODERN  STEAM  ENGINES. 


and  it  is  a  disputed  point  among  engineers,  as  to 
whether  this  is  an  evil  or  not.  If  it  is  considered  desir- 
able we  may,  however,  to  a  great  extent,  equalize  the 
lead  for  the  forward  gear,  by  moving  the  two  eccentrics 


the  forward  stroke.  The  positions  of  the  link,  are 
found  by  the  method  given  in  the  previous  examples, 
and  it  is  seen,  that  putting  the  eccentrics  forward,  \vill 
not  affect  the  lead  in  mid-gear,  since  it  merely  swings 


Fig.  99. 


Fig.  100. 


forward  upon  the  shaft,  and  adding  steam  lap  to  the 
valve.  In  Figs.  99  and  100,  for  example,  we  have  the 
center  lines  of  the  parts,  and  the  positions  of  the  link, 
when  in  full  gear  and  in  mid-gear.  In  both  cases,  the 
parts  are  drawn  in  dotted  lines,  and  also  in  full  lines. 

The  dotted  lines  represent  the  eccentric  and  link,  drawn 
in  their  normal  positions,  while  the  full  lines  represent 
the  eccentrics  moved  forward,  to  equalize  the  lead  on 


the  link  on  its  pivot  at  in,  fiut  in  full  forward  gear, 
moving  the  eccentrics  forward  increases  the  lead  of  the 
valve,  making  it  equal  to  the  lead  at  mid-gear;  the 
amount  of  increase  of  lead,  due  to  moving  the  eccen- 
trics, being  equal  to  the  radius  c  c'. 

Suppose,  now,  that  as  in  the  case  of  our  previous  ex 
amples,  the  eccentrics  are  set  in  their  normal  positions, 
and  the  lead  at  full  gear,  is  $  inch,  and  we  see  in  the 


LJ\/\   MOTIONS. 


81 


diagrams,  Figs.  88,  and  94,  that    at    mid-gear  it  had  in- 

1    tn   y  inch.     But  we  may  add  to   the  valve  suf- 

ia|i  to    reduce    its   1,-ad  to    |  inch  mid-gear,  and 


'I'liis  equalization,  however,  is  only  obtained  at  the 
expense  of  the  backward  gear,  as  may  lie  seen  from  Fig. 
101,  in  which  tint  link  is  placed  in  full  gear  backward, 


Fig.  101. 

then  set  the  eccentrics  forward,  so  as  to  give  ±  lead  in  I  and  it  is  seen  that  moving  the  eccentrics  forward  has 
full  gear,   Fig.    99    showing   that   putting    the   eccen-  |  reduced  the   lead.     If  the   amount   the  eccentrics   are 


trics  forward,  will  not  affect  the  lead  at  mid-gear,  and  it 
being  obvious  that,  for  full  gear,  we  must  set  the  eccen- 
trics forward  enough  to  compensate  for  the  £  inch  lead 
that  has  been  added,  and  thus  equalize  the  lead  for  the 
forward  gear. 


Fig.  102. 

moved  forward  is  sufficient  to  about  equalize  the  lead 
for  forward  gear,  it  must  have  been  sufficient  to  move 
the  valve  -fa,  when  in  full  forward  gear,  and  ^  inch  of 
lap,  would  require  to  be  added  to  the  lap,  and  it  is  evi- 
dent that  if,  with  the  eccentrics  in  their  normal  posi- 


82 


MODER^7  STEA  M  EXG1NES- 


tions,  there  is  \  lead  at  full  backward  gear;  then  moving 
the  eccentrics  ahead,  will  have  left  but  fa  inch  lead,  in 
the  full  backward  gear,  hence  we  find  that  equalizing 


pond  to  those  used  in  previous  figures,  and  we  find  the 
position  of  the  parts  by  the  same  means  as  in  previous 
examples  except  as  follows.  Having  marked  from  s 


Fig. 

the  lead  for  the  forward    gear,  gives  -J-  inch    lead    at 
mid-gear,  and  but  -fa  inch, in  the  full  backward  gear. 

LIXK  MOTION  WITH  CROSSED  RODS. 

Figs.  102,  and  103,  represent  a  link  motion  with 
crossed  rods,  the  rods  being  crossed  when  the  crank  is 
on  the  dead  center  B,  and  open  when  it  is  on  the 
opposite  dead  center. 

In  this  case,  the  link  is  brought  above  the  line  of 
centers  when  in  full  gear,  instead  of  below  it,  as  in  the 
case  of  open  rods. 

This  occurs,  because  the  forward  eccentric  is  connect- 
ed to  the  lower  end  of  the  link,  and  as  a  result,  the  re- 
versing lever  requires  to  be  pulled  backward,  in  order 
to  put  the  link  in  forward  gear,  and  vice  versa.,  whereas 
in  open  rods  the  reversing  lever  is  moved  forward,  for 
forward  gear,  and  backward,  for  backward  gear. 

The  same  eccentric  (that  which  leads  the  crank),  is 
still,  however,  the  acting  one,  as  may  be  seen  by  compar- 
ing Fig.  103,  with  Fig.  81,  both  being  for  full  forward 
gear,  and  eccentric  e,  in  both  cases  operating  the  valve. 

In  Fig.  103,  the  lines  and  letters  of  reference,  corres- 


103. 

(and  with  the  radius  from  the  center  of  the  eccentric  to 
the  center  of  the  link-slot),  as  a  center  the  arc  a,  and 
from  t  as  a  center  the  arc  d,  and  having  drawn  / 1  mid- 
way between  a  and  d,  we  then  take  the  length  of  the 
link-hanger,  and  mark  arc  to,  and  where  this  arc  cuts 
line  I,  is  the  line  q,  on  which  the  lifting-shaft  arm  will 
fall  for  the  mid-gear. 

We  then  draw  the  lifting-shaft,  and  from  its  center  S, 
draw  the  arc  y  y'.  Turning  now  to  the  full  gear  with 
crossed  rods  (Fig.  103),  we  mark  in  the  position  of  the 
parts  by  the  same  means  as  in  previous  examples,  and 
with  the  length  of  the  link-hanger  as  a  radius,  and  from 
the  center  m  of  the  link,  we  draw  arc  r,  giving  us  the 
point  of  suspension  of  the  upper  end  of  the  link  hanger. 
"We  may  then  take  the  same  radius,  m,  x,  of  the  full 
gear,  and  mark  from  m  the  point  v,  which  is  the  point 
of  suspension  for  full  backward  gear.  It  is  shown 
therefore,  that  in  crossed  rods,  the  points  x,  and  v,  are 
equidistant  from  w,  which  is  not  the  case  with  open 
rods. 

The  proof  is,  that  we  may,  by  means  of  a  dotted  arc, 
find  the  position  of  the  saddle-pin  when  the  link  is  in 


/./.YA'  MOTIONS 


full  backward  gear,  thi<  point  beini:  at  /<  in  Fiir  UK;,  nnd 
it  will  !»•  found  in  that  figure,  that  the  di-tances  from 
)'  In  V,  from  C,  tn  ID,  an. 

of  the  link  hanger  when  in  full 
r  forward,  full  gear  backward,  ami  mid-gear 
ectively. 

we   may     prove  the   construction  from   the 
mill  gear  as  follows: 

A\  Ken  the  link  is  in  mid-gear,  the  hanger  stands  from 
f  full  gear  forward,  tin-  center  of  the  saddle-pin, 
e  of  the  link,  will  lie  at  m.  and  tho  hanirer 
will  stand  at  m  j-\  at.  full   gear   bad  ward,  the   center  of 
the  saddle-pin  will    he  at  i>.  and  the  hanger  from/)  to  9; 
-  radii  r.  ir,  p.  r.  and  m   ''are  equal,  while  j  and  r.  are 
equidistant    from  ir.  whicn  it  has,  been  shown  is  n.>: 
case  with  open  rods. 

T1IK  VAKIATIOX  OF  LKAD  IX    CKOSSKII    RODS. 

It  may  now  lie  pointed  out.  that  in  the  case  of  crossed 

rods  the    lead  is  diminished    by    moving   the  link   from 

full  gear  to  mid-gear,  (instead  of  being  increased  as  was 

with  open   rod-),  and   this  may  be  shown  as 

follows: 

1 1'.  with    the  radius   from  the  .center  of  the  respective 

ntricB,  to  the  center  of  the  link-slot,  we   murk   the 

p  and  n  n'.  Fig.  lo-_>.  we  get  at  their  inter- 

ion  on  the  line  of  centers,  the  position  of  the  center 

the  link-Mock  when  the  link  is  in  full  gear  either  for 

.ward  or  forward  motion,  and  the  figure  shows  that 

the  link-block,  in  mid-gear,  stands  at  c,  hence  the  lead 

decreased  the   amount   represented  by  the  distance 

from    the   intersection  (on  the   line   of  centers)   of 

i  arcs  p  p,  with  arc  «  n'. 

EQUALIZING  THE  LEAD  WITH   CROSSED   BODS 

\Ve  may.  however,  equalize  the  lead,  by  putting  the 
nirics  an  equal  amount  backwards  upon  the 
which  will  have  no  effect  upon  the  lead  at  mid- 
hut  will  decrease  it  for  the   full  forward  gear. 
Thus  in  Fig.  104,  the  parts  are  shown  in  mid-gear,  the 
normal  fiosition  of  the  eccentrics  and  link,  being  shown 

in  dotted  lines,  and  their  positions  with  tl ccentrics 

put  back,  shown  in  full  lines.     By  the  methods  before 
II 


described,   we   find   tin-  pillion   of    the  link    with    the 

ntrics  at  e  and  f.  an  ion  with  the  eccen- 

.11   >•'/',  and  as  the    center  of  the  link  slot,    and 


-  m-  / 


Fig.   104. 

therefore  of  the  saddle-pin,  falls  at  r  on  the  line  of  centers 
in  both  link  positions,  it  is  clear  that  altering  the  position 
of  the  eccentrics  does  not  move  the  link  center,  where- 
as in  full  gear  it  is  obvious  that  moving  the  eccentric 
back  will  decrease  the  lead,  and  we  may  therefore  reduce 
the  amount  of  steam  lap  so  as  to  give  the  requisite 


Fig.   105. 


amount  of  lead  which  will  remain  perfectly  the  same 
at  all  points  in  the  forward  gear,  and  up  to  mid-gear. 
But  this  will  disarrange  the  lead  for  the  backward  gear 
as  may  be  seen  from  Fig.  105,  in  which  it  is  seen  that 
setting  the  eccentrics  back  from  the  dotted  to  the  full 


MODERN  STEAM  ENGINES. 


lines,  brings  the  link  back  from  the  dotted,  to  the  full 
lines  and  as  the  crank  is  on  the  dead  center  D,  this 
increases  the  lead,  whereas  in  the  forward  gear  it 
decreases  it,  and  it  follows  that  the  equalization  of  the 
lead  by  means  of  moving  the  eccentrics,  and  adjusting 
the  lap  to  suit,  is  only  permissable  when  the  engine  per- 
forms its  principal  duty  while  running  in  one  direction, 
because  to  whatever  amount  we  improve  the  lead  in  one 
full  gear,  we  derange  it  in  the  other  full  gear.  The 
port  openings  and  closures,  are  practically  the  same  for 
corresponding  points  of  cut-off,  whether  the  rods  are 
crossed  or  open. 

LINK    MOTION'    WITH    THE    ALLEX    VALVE 

\Ve  may  greatly  improve  the  steam  admission,  whether 


sp 

> 

< 


s 


\ 


\ 


\ 


Fly.    10(5. 

the  link  motion  has  either  open,  or  crossed  rods,  by 
employing  the  Allen  valve  in  place  of  the  common  slide 
valve. 

The  construction  of  the  Allen  valve,  has  been  shown 


^ 


\ 


\ 


\ 


\ 


Fig.   107. 

in  the  engravings  from  Fig.  31,  to  Fig.  43,  but  it  is 
for  the  shorter  points  of  cut-off  that  it  possesses  its 
greatest  advantages. 

By  substituting  an  Allen  valve  on  the  open   rod  link 


motion,  shown  in  Fig.  78,  and  of  the  proportions  already 
given,  we  obtain  the  port  openings  given  in  Figs.  106, 
and  107. 

As  the  Allen  valve  is  double  ported,  we  may  obtain 
the  £  inch  lead  at  full  gear  that  was  given  in  previous 
examples,  by  giving  the  valve;  -J,  inch  lead,  the  two  ports 
giving  an  amount  of  lead  opening  equal  to  the  ^  inch 
of  a  single  port,  hence,  we  set  the  eccentrics  back,  redu- 
cing their  angular  advance  sufficiently  to  alter  the  lead 
from  4^,  to  ^  inch. 

The  superior  admission  of  the  Allen  valve  is  obtained 
as  follows: 

In      Fig.     108,     the     port    K    is    shown     open     to 


10S. 


the  amount  of  the  lead,  and  as  this  is  i  inch  only,  the 
eccentric  is  in  a  better  position  to  open  the  port  quickly, 
having  a  less  angular  advance,  and  being  more  nearly 
at  a  right  angle  to  the  crank,  than  would  be  the  case  if 
the  lead  at  g  were  4^  inch.  Nevertheless  the  effective 
lead  is  4^  inch,  because  there  is  ^  inch  opening  at  //.  as 
well  as  at  g. 

When  the  valve  moves  ,the  effective  opening  remains 
at  double  the  opening  at  g,  until  the  valve  reaches  the 
position  shown  in  Fig.  109,  the  opening  at  g,  and  at  e 
then  being  equal,  and  after  this,  the  amount  of  effen 
port  opening  will  remain  constant  or  equal,  until  the 
supplementary  port  is  closed  as  in  Fig.  110,  because  we 
see  in  Fig.  109,  that  to  whatever  amount  e  closes  (as  the 
valve  moves  to  the  right),  the  opening  at^  will  increase. 
thus  maintaining  an  equal  amount  of  port  opening, 
while  the  valve  moves  from  its  position  in  Fig.  10!>,  to 
its  position  in  Fig.  110.  This  period  of  equal  port 
opening  is  shown  on  the  diagram,  Fig.  106  at  a,  after 
the  valve  has  reached  the  position  shown  in  Fig.  1  1  n. 


7./.VA" 


85 


tin'  port  i. ncmii;;  is  governed  by  the    outer  edge  only  of 
•  •Mtary    port    being   cWed.  henee 
-ion   from   •/,  to    full    !"  ' 

.limn  Mide  \alve  \vuuM  •  .\iding   i' 

4  inch  lead. 

When  tin-  \:i  iiploted  its  stroke,  and  returns 

to  close  the  port.  and    elTect    tin1  cut-off,  the   amount    of 


Fig.   ion. 

port  opening  is  the  same  as  f.u-  an  ordinary  slide  valve, 
until  tin'  valve  has  reaelied  the  position  in  Fig.  Ill,  this 
perio.l  being  shown  in  the  diagram  Fig.  10R.  from  c  to 
this  point,  the  supplementary  port  will 
again  conn-  into  action,  maintaining  the  port  opening 


Fig.   lin. 

oniial.  until  the  valve  has  moved  to  the  position  shown 

in  Fig.  110.     This   equal    amount   of  port   opening,  is 

vn  in  the  diagram,  Fig.  106,  from  </,  to  e;  d  being 

for  the  valve   position  in  Fig.  110,  and  c,   for  the  valve 

in  Fig.  111.     After  this  point,  the  amount  of 

'•loses  as  fast  as  that  at  g,  but  the  effective 

•ling  still   remains    double    what   it  would  be,   in  a 

common  slide  valve. 

The  port  openings  for  tb»  Allen  valve,  when  the  link 


i-  hooked  up  to  cut  off  at  half  stroke,  are  shown  in 
l-'ig.  ln~.  and  it  is  seen  ihat  ihr  admi>sion  is  very  much 
superior  to  ;  •  -.ed  with  a  common  si: 

as  may  be  seen   b\  --g    l-'ig.   HIT,  to  l-'i^,.-.  HI,  or 


Fi<j.  111. 

95.  This  superiority  is  maintained  both  at  quarter  cut- 
off, and  at  mid-gear,  as  may  he  seen  on  comparing  Figs. 
111.  and  111',  with  Figs.  !)•_'  ami  !)4. 

INOIIK.ASK  OF    LEAD  WITH  THE  ALLEN  VALVK. 

The  Allen  valve,  it  may  be  observed,  increases  the 
lead  more  than  the  common  valve  when  the  link  is 
hooked  up,  thus  at  half  stroke,  the  lead  is  $  for  the 


"~N 

\ 

x 

§ 

\ 

/ 

s 

\ 

^ 

\ 

/ 

' 

j 

s 

\ 

1 

; 

5 

3 

Fig.  112. 

edge  of  the  valve,  and  f  for  the  supplementary  port,  or 
a  total  of  £  inch.  We  may,  however,  equalize  the  lead 
for  the  forward  gear  (at  the  expense  of  the  backward 
gear),  by  the  construction  explained  with  reference  to 
figures  99  and  100.  Similarly,  if  crossed  rods  be  used 
for  the  link  motion,  we  may  equalize  the  lead,  by  means 
of  moving  the  eccentrics  back,  as  already  explained; 
but  it  is  to  be  noted  that,  as  there  are  two  ports,  and  | 
inch  of  actual  valve  lead  becomes  ^  inch  of  effectual 
valve  lead,  therefore,  with  ^  actual  valve  lead  (the 


€&SE   LIB 
OF  THE 
EVERSITY 


SG 


J/o/JAY-.'.V  STEAM  ENGINES. 


eccentrics  not  being  set  back  to  equalize  the  lead),  the 
purls  would  come  blind  quicker  when  the  link  is  moved 
towards  mid-gear,  tnaii  would  be  the  case  with  the 
common  valve,  having  the  same  amount  of  effectual 
lead.  This  corresponds  to  the  action  of  the  Allen  valve 
in  increasing  the  .ead  to  a  greater  amount  when  the 


\ 

X 

N 

\ 

/j 

/ 

1 

si 

\ 

/I 

^ 

Fig.    11J5. 

link  lias  open  rods,  and  is  moved  towards  mid-gear. 
But  as  the  eccentrics  have  less  angular  advance  for  a 
given  effective  amount  of  lead  in  the  Allen,  than  in  the 
common  valve,  therefore  they  are  in  a  better  position 
for  being  moved  to  equalize  the  lead,  if  such  be  desired. 

LINK  MOTION. 


In  Gooch's  link  motion,  the  arc  of  the  link  is  in  the 
opposite  direction  to  that  of  Stephenson's  link  motion, 
as  will  be  seen  in  Fig.  114.  The  hanger  is  pivoted  at 
its  upper  end  to  a  fixed  pin,  and  the  direction  of  valve 


114. 


motion  is  reversed  by  moving  the  link-block,  which  is 
upon  an  arm  that  is  pivoted  at  P,  to  the  slide  spindle, 
the  lifting-shaft  arm  being  connected  at  D. 

Fig.  115,  shows  the  parts  in  full  gear  for  the  back- 


ward motion,  the  crank  being  on  the  dead  center  IB. 
Shorter  points  of  cut-off  are  obtained  by  lifting  the  arm 
E,  and  therefore  the  link-block,  nearer  to  the  line  of 
centers,  or  to  the  saddle-pin.  The  lifting-shaft  S,  is  at- 
tached to  the  arm  E,  and  the  curve  of  the  link-slot  is 
an  arc  of  a  circle,  of  which  the  length  of  arm  E  is  the 
radius.  As  the  link  stands  at  a  right  angle  to  the  line 
of  centers,  when  the  crank  is  on  either  dead  center,  the 
lead  is  maintained  equal,  it  1  icing  obvious  that  the  link- 
block  can  (with  the  link  at  a  right  angle  to  the  line  of 
centers),  be  moved  from  end  to  end  of  the  link,  with- 
out imparting  any  motion  to  the  valve  spindle  A. 

The  position  necessary  for  the  upper  end  of  the  link 
hanger,  in  order  to  thus  equalize  the  lead  for  all  points 
of  cut-off,  may  be  found  as  follows: 

In  Fig.  115,  let  e  and  f,  represent  the  center  lines  or 
throw  lines,  of  the  two  eccentrics,  whose  positions  for 
any  given  amount  of  lap  and  lead,  may  be  found  as  in 
previous  examples,  and  with  a  radius  equal  to  the  length, 
from  the  center  of  the  eccentric  to  the  center  of  the 
link-slot,  we  mark  from  e  the  arc  n,  and  from/  the  an; 
in.  From  the  line  of  centers  1)  b,  we  mark,  with  a  radius 
equal  to  the  length  of  the  link  (measured  from  one 
extreme  link-block  position  to  the  other),  the  two  arcs 
p  and  p',  and  these  are  the  ends  of  the  link.  With  the 
radius  of  the  arm  E,  and  from  a  point  jc,  on  the  line  of 
centers,  wo  mark  in  the  position  of  the  center  line  of 
the  link,  when  the  crank  is  on  its  dead  center  furthest 
from  the  cylinder.  Then  with  the  radius/;/;,  and  from 
/'  as  a  center,  we  mark  arc  mf,  and  from  e'  the  arc  //, 
giving,  at  their  intersections  with  the  arcs  //  //  re- 
spectively, the  positions  of  the  ends  of  the  link  when 
the  crank  is  on  its  dead  center  D. 

From  the  ends  of  the  link  when  in  this  position,  and 
with  the  length  of  arm  E  as  a  radius,  we  find,  on  the  line 
of  centers,  the  point  Z,  which  is  the  center  from  which 
the  center  line  of  the  link  (when  the  crank  is  on  dead 
center  D),  may  be  drawn. 

We  have  thus  found  the  two  link  positions  for  the 
two  crank  dead  centers,  and  mid-way  between  them  we 
draw  the  line  I,  on  which  the  upper  end  of  the  link 
hanger  must  stand,  and  to  find  the  heighth  at  which  it 
must  stand  from  the  line  of  centers  b  !>,  we  take  the 
length  of  the  link  hanger,  and  from  a,  (the  center  of 
the  link  in  one  position),  on  the  line  of  centers  mark 


A/.YA"  MOT!n\s. 


87 


</.     Tlii-n  from  :/.  (tin-  center   cf  tin-  link   in  the 

oilier  "ii  tin'  lini-  of  centers,  we   mark  are  </', 

iiii'l  \\  x  cut   tin-  line  /.  is  tlie  position    for 

•  1  the    pivot,  fruin    which    the    link    hanger 


on  tin-  lino  of  centei-s.  and  the  link  will  be  vertical, 
hence  the  link-block  may  be  moveil  from  end  to  end 
of  the  link  without  imparting  any  motion  to  the  valve 
spindle.  To  find  the  positions  for  the  lifting-shaft  and 


must  be  suspended.  The  arc,  in  which  the  link  hanger 
will  swinjr,  is  denoted  by  arc  F  F,  which  crosses  the 
line  of  centers  at  a  and  d,  so  that  when  the  crank  is  on 
either  dead  center,  the  center  of  the  saddle-pin  will  be 


118. 

its  arms,  we  take  the  radius  D  P,  and  from  P  as  a  center, 
mark  a  point  r  on  the  lino  of  centers,  and  from  r,  erect 
a  perpendicular  r  r';  then  take  the  length  of  arm  G, 
and  from  r  mark  an  arc  v,  and  from  the  intersection  of 


88 


MODERN  STEAM  ENGINES. 


v  with  r  r',  draw  a  line  t,  then  from  v,  mark,  with  the 
length  of  the  arm  II,  the  center  S  for  the  lifting-shaft. 
From  S,  as  a  center,  the  arc  K  may  be  drawn,  and  then 
with  the  length  of  G  as  a  radius,  and  from  D,  as  a  center 
wo  mark  at  g,  on  the  arc  K,  the  position  of  the  upper 
end  of  the  arm  G.  When  the  link-block  is  in  mid- 
gear,  the  arm  E  will  be  parallel  with  the  line  of  centers, 
and  the  position  of  G  will  be  from  r  to  v  (at  a  right 
angle  to  the  line  of  centers),  and  we  may  therefore  take 
the  radius  v  g,  and  from  v,  as  a  center,  mark  arc  //,  the 
position  of  arm  II,  when  in  full  gear  for  the  forward 
motion  ;  hence  the  three  positions  for  arm  H  are  :  II ; 
on  the  line  t;  and  at  H'  and  the  corresponding  positions 
for  the  upper  arm  of  the  lifting-shaft,  are  J,  J',  and  J". 
The  points  of  cut-off,  with  a  Gooch  link  motion  thus 


construced  will,  vary  to  an  amount  depending  upon  the 
proportion  the  length  of  the  connecting-rod  bears  to 
the  length  of  the  stroke,  as  in  all  previous  examples 
and  if  we  were  to  move  the  positions  of  the  eccentrics 
(as  was  done  in  Figs.  99,  100  and  101)  in  order  to 
equalize  the  points  of  cut-off  for  either  gear,  the  lead 
will  no  longer  be  equalized  because  the  link  will  not 
stand  vertical  when  the  crank  is  on  the  dead  center  ; 
lience  moving  the  arm  E,  Fig.  115,  up  and  down  the 
link  will  impart  motion  to  valve  spindle  A  and,  there- 
fore, to  the  valve,  thus  altering  the  lead.  The  points  of 
cut-off  may,  however,  be  equalized,  and  the  lead  main- 
tained equal,  by  making  one  steam  port  wider  than  the 
other,  as  will  be  explained  in  connection  with  a  link 
motion  having  a  rocking-shaft. 


Fig.   116. 


CHAPTER    IV. 


;XJNIVERSI 

OF 


LIXK   MUTIIINS  WITH    HOCK  SHAFT. 


Fig.  116  represents  a  link  motion  such  as  is  used  on 
American  locomotives,  the  parts  being  shown  in  posi- 
Iioii  witli  the  crank  on  the  dead  center  1!.  and  with  the 
link  in  full  forward  gear.  The  link-block  is  carried 
upon  the  lower  arm  II  of  a  rocker,  rock-shaft,  or  rocking- 

:.  as  it  is  promiscuously  termed.  The  upper  arm 
K  of  the  rocker  drives  the  valve  through  the  medium 

•;.•  valve  rod  or  valve-spindle  R.  The  valve,  there- 
fore, moves  in  the  opposite  direction  to  that  in  which 
tne  link-block  moves  and  the  eccentrics  are  therefore 
;ii  an  angle  of  less  than  90°  to  the  crank.  The  amount 
to  which  they  are  less  than  90°  is  the  angular  advance. 
When  the  crank  is  at  B,  thrt  valve  must  move  in  the 
direction  of  its  arrow  in  order  to  open  the  port  A  for 
the  admis-ion  of  the  live  steam,  and  as  the  arm  G, 
which  carries  the  link-block,  must  move  in  the  oppo- 

di  reft  ion  to  the  valve,  it  is  ch'nr  that  it  is  the  eccen- 
tric /'  (which  follows  the  crank)  that  must  be  connected 
to  the  upper  end  of  the  link,  and  hence  the  eccentric 

crossed. 

Instead  of  a  weight  being  used  to  counterbalance  the 
link.  etc..  the  rod  L  connects  to  a  volute,  or  coiled, 
spring  which  acts  instead  of  the  weight. 

THE    OFF-SET    OF    THE    ROCKER- ARM. 

The  center  line  of  the  engine  is  on  the  line  h  b,  and 
it  is  seen  that  the  center  of  the  link-block  is  below  it 


on  the  line  c  c,  a  condition  that  commonly  prevails  in 
American  locomotives. 

This  necessitates  that  the  two  arms  P  G  of  the  rocker 
lie  thrown  out  of  line  one  with  the  other,  in  order  that 
the  motion  of  the  valve  may  be  equal  at  all  parts  of  the 
stroke,  to  that  of  the  link  block. 

The  upper  arm  F  of  the  rocker  moves  the  valve  in  a 
lino  parallel  to  the  line  of  centers,  and  therefore  stands 
vertical  when  in  its  mid-position,  while  the  lower  arm  G 
stands,  when  in  mid-position,  at  an  angle  to  the  line  of 
centers  b  b,  the  amount  of  this  angle  being  called  the 
off-tel. 

To  find  the  amount  of  off-set,  we  proceed  as  in  Fig.  1 1 7, 
in  which  the  parts  are  represented  by  their  centers  and 
center  lines  and  the  letters  of  reference  correspond  to 
those  in  Fig.  116.  The  line  of  centers  b  b  being  drawn, 
we  draw  the  circle  n,  its  radius  equaling  the  throw  or 
the  eccentric,  and  its  diameter  the  travel  of  the  valve 
when  the  link  is  in  full  gear.  From  the  center  of  circle 
n  (and  with  a  radius  equal  to  the  distance  between  the 
center  of  the  axle  and  that  of  the  rock-shaft)  we  draw 
an  arc  n,  and  on  this  arc  measure  below  line  b  b  the 
distance  the  link-block  is  to  stand  below  the  line  b  b 
when  the  arm  G  of  the  rocker  is  as  its  lowest  point, 
and  through  this  point  draw  line  c  c.  Or,  instead  of 
this  construction,  we  may  assume  a  point  a  and  mark 
it  by  a  dot,  then  draw  above  it,  and  at  the  required  dis- 

89 


90 


MODERN  STEAM  EXCJXES. 


tance,  the  line  of  centers  b  b,  and  on  it  mark  the  circle 
n;  line  C  C  may  then  be  drawn,  passing  through  the 
dot  a  and  the  center  of  circle  n.  At  a  right  angle  to 
C  C,  and  through  the  dot  at  a  we  mark  a  line  a,  which 
will  be  the  center  line  of  the  lower  arm  of  the  rocker 
when  it  is  in  mid-position.  From  a,  as  a  center,  and 
with  the  length  of  the  lower  arm  of  the  rocker,  as  a 
radius,  we  draw  an  arc  c  c,  and  where  this  arc  cuts  line 
n  is  the  center  of  the  rocker-shaft.  From  this  center. 
we  draw  arc  t  t,  on  which  will  be  the  path  of  motion  of 
the  lower  end  of  the  rocker-arm,  or,  what  is  the  same' 
thing,  the  path  of  motion  of  the  link-block,  and  this 
path  of  motion  will  be  an  equal  distance  on  each  side  of 
line  a. 


tremes  of  motion  of  the  lower  rocker  arm  when  tho 
link  is  in  full  gear  for  either  the  backward  or  the  for- 
ward motion.  At  a  right  angle  to  the  line  of  centers, 
and  from  the  arcs  p  p,  we  draw  lines  u  «',  and  where 
these  cut  the  arc  t'  t',  are  the  extremes  of  motion  of 
the  eye  of  the  upper  arm  when  the  link  is  in  full  gear. 
By  this  construction,  the  lower  arm  G  of  the  rocker 
vibrates  in  an  arc  that  is  equalized  with  the  line  C  C, 
from  which  it  receives  its  motion,  while  the  upper 
rocker-arm  F  vibrates  in  an  arc  that  is  equali/.ed  with 
the  line  in  which  it  delivers  its  motion,  or,  in  other 
words,  the  line  of  motion  of  the  slide  valve,  the  valve 
face  being  parallel  to  the  line  of  centers.  If  the  valve 
face  were  at  an  angle  to  the  line  of  centers,  then  lines 


7? 


*' 


/ 


.& 


J 

1    r. 

k    u 

43 

Tc 
>fi  \  '] 

k  \ 

K  \i 

t                  ^^ 

<? 

—  S4_ 

y 

-i—  =i 
f 

. 

£f 


Fig.    117. 


From  the  center  of  the  rocker,  and  at  a  right  angle 
to  the  line  of  centers  b  b,  we  draw  a  line  d,  which  will 
be  the  center  line  of  the  upper  arm  F  of  the  rocker 
when  it  is  in  mid-position.  From  the  center  of  the 
rocker,  and  with  the  length  of  the  upper  rocker-arm  as 
a  radius,  draw  an  arc  t'  t',  on  which  will  be  the  path  of 
motion  of  the  eye  of  the  upper  arm  of  the  rocker, 
which  will  vibrate  on  this  arc  and  an  equal  distance  on 
each  side  of  line  d. 

To  locate  the  length  of  arc  through  which  the  rocker- 
arms  will  vibrate  when  the  link  is  in  full  gear,  we  draw, 
from  the  center  of  the  rocker-shaft,  two  arcs  p  p,  their 
radius  equaling  that  of  the  circle  «,  and  from  these 
arcs  we  draw  lines  q  q'  at  a  right  angle  to  the  line  c  c, 
and  where  these  lines  cut  the  arc  t  t  will  be  the  ex- 


d,  u  and  u'  would  require  to  be  at  a  right  angle  to  the 
valve  seat  or  valve  face. 

The  action  of  the  link  motion  is  not  in  the  least  in- 
fluenced by  the  off-set  in  the  rocker-arms,  providing 
that,  as  in  this  construction,  the  mid  position  of  the 
lower  rocker-arm  is  at  a  right  angle  to  C  C,  and  that 
of  the  upper  arm  is  at  a  right  angle  to  b  b,  and  the 
action  is  the  same  as  if  the  center  of  the  link-block, 
when  at  its  lowest  point,  came  coincident  with  line  b  b. 
and  there  were  no  off-set  in  the  rocker-arms. 

To  find  the  posit  tons  of  the  eccentrics,  we  mark  from  the 
point  a,  on  the  line  C,  and  with  the  steam  lap  and  lead  as 
a  radius,  an  arc  g,  and  where  g  cuts  arc  /,  is  the  position 
of  the  center  of  the  link-block  (or,  what  is  the  same 
thing,  the  position  of  the  eye  in  the  lower  rocker  arm) 


/./.VA'  .\furtu\x  \vrrii 


sn.\rr. 


91 


when  the  crank   is  on   its  dead  center   H.       From   this 
center,  and    willi    the   length   of  tlie   ec-cenn 
radius,  we    mark    across    the    circle    //    an    arc  /   r,    and 
•  R,  are    the    position!  tot  the  BCC8B- 

M    marked    at  ••ami   at    /'.      In    I'V-   lls.  the   con- 


nives the  eccentric   positions  when  the  crank  is  on  the 

te  dead  center. 

Tn  tinil  ilf  position  "f  ili:-  rocker-arms. — When  the 
crank  is  on  its  doat  1  center  B,  tho  valve  will  obviously 
have  moved  from  its  mid  position  over  the  ports  to  an 


/•;;•/.  us. 


struction    is    rejieatcd    for   both    strokes,  the   eccentric 
us  Ijein^   found    l>v  marking  arcs  g  g'  on    t 
.ait  from  «  to  the  amount  of  the  lap  and  the  lead  ; 


amount  equal  to  the  lap  and  the  lead,  and  the  rocker- 
arms  will,  therefore,  also  have  moved  from  their  mid- 
positions  to  the  amount  of  the  lap  and  the  lead,  hence 


arc  r  r  (drawn  from  g,  with  the  length  of  the  eccentric- 
-  a  radius)  giving  the  eccentric  positions  when  the 
crank  is  at  B,  and  arc  r'  r'.  drawn  from,  g'  on  the  arc  t, 
12 


119. 


the  lower  arm  will  be  at  g,  and  the  upper  arm  at  n', 
which  is  distant  from  d  to  the  amount  of  the  lap  and 
the  lead. 


92 


MODERN  STHAM  /•: X 


To  find  the  position  of  the  link  corresponding  to  crank 
position  B. — In  Fig.  119,  we  have  the  center  lines  of  the 
parts  (omitting  the  lines  used  to  find  their  positions), 
the  link  being  in  full  forward  gear,  and  it  is  found  that 
the  center  of  the  link  arc  is  at  e,  or,  in  other  words,  the 


drawn  from  the  center  of  the  eccentric  that  leads  the 
crank. 

To  find  the  position  of  the  parts  when  the  link  is  in  nui- 
year.— From  /  Fig.  121,  as  a  center,  and  with  a  radius 
from  a,  on  the  line  of  centers  C  C,  to  the  center  of  the 


V    \> 


120. 


center  of  the  eccentric  that  leads  the  crank,  whereas,  in 
open  rods,  it  is  the  center  of  the  eccentric  that  follows 
the  crank.  Fig.  120  shows  the  parts  in  position  for  full 
gear  backward,  and  it  is  seen  that  the  center  of  eccen- 


crank  shaft,  we  mark  an  arc  E  g,  somewhere  on  which 
we  know  the  upper  end  of  the  link  will  be.  With  '.!„• 
same  radius,  and  from  e  as  a  center,  draw  an  arc  H  y, 
and  where  these  arcs  cut  arc  t  (or  at  point  g)  is  the  posi- 


trie/,  that  leads  the  crank,  is  that  from  which  the  link 
arc  may  be  drawn  ;  hence  we  have  that  with  the  link 
in  full  gear,  and  the  crank  on  the  dead  center  for  either 
the  forward  or  backward  motion,  the  link  arc  may  be 


tion  of  the  link-block  when  the  link  is  in  full  gear  for 
either  the  forward  or  the  backward  motion. 

From  g,  as  a  center,  we  mark  arcs  w  and  w'  for  the 
ends  of  the  link,  and  from  the  points  of  intersection  of 


LL\K  MOTIONS    117/77   ROCK  xil 


93 


e  arcs  with  arcs  E  and  II  respectively,  and  with  a 
radius  from  n   (on   the   line  C  C)    to    the   centor  of  the 
ik  shaft,  we   mark    ;uv    /i  A',  giving  at    I  tlie  center 
from  which  the  link  arc  may  bo  drawn. 

at   the  eenter  df   the    link    will    depend 

in   the   point  of  suspension   of  the    link   hanger.      If 

lifl  hanger  to    lie  suspended  lit,  a  ]>oint  eoin- 

nt    witli     the    eenter    nf    l!u;    rocker,  then     the    link- 

the    link  block,  will  move   on    the  arc 

:ersof   boili  will    be  nt  '•  ;   we  must  there- 

tore  murk  new  arcs  ,r  and  r'  fur  liie  ends,  of  the!  link. 

/'/(••    incrtas    of   lead.  —  It    will  now    be   seen    that,    in 

moving  the  link  tro:n  f;i!l  gear   to    mid  gear,  the  center 

ik-block  and  of  the  lower  rocker-arm  is  moved 

,  •/  in  v,  and  this  moves  the  valve   forward,  incroas- 


action,  therefore,  so  far  as  tlin  load  is  concerned,  is  the 
as  a  link  motion  with  open  rods  and  no  rocker. 

'/'A.  ,     nf    tin;     Jink     /Kiiii/fi: — The 

jioints  of  sn.~p'  link-hanger  may  be  lncate<l 

with  a  view  to  either  givo   the    least    amount,  of  sliding 
moiion  of  the  link-block   in  the  link  slot,  and  obtain  at 

•  the  widest  amount  of  port  opening,  or,  in 

second  case,  to  equalize  the  points  of  cut-oil  for  the 
two  strokes.  T<>  find  ihe  points  of  suspension  for  the 
amount,  of  sliding  motion  of  the  link-block,  and 
for  the  widest  port  opening,  we  proceed  as  in  Fig.  123, 
in  which  the  link  is  shown  in  two  positions,  viz.,  full 
gear  for.vard  and  mid-gear,  and  i:  is  obvious  that  the 
link  suspension  would  be  the  mos-t  perfect  f  >r  the  full 
forward  gear,  if  the  upper  end  of  the  link  hanger  Lad 


Fig.   122. 


ing  the  lead,  the  same  as   in  link  motions  having  open 
-  and  no  rocker.     This  only  occurs  with  crossed  rods 
when  a  rocker  is  used.     The  upper  end  of  the  rocker- 
arm  obviously  stands  to  the  right  of  the  line  d  to  the 
same  amount  as  the  lower  arm  stands  to  the  left  of  line 
In  Fig.  122.  the  link  is  in  mid-gear,  with  tho  crank 
'  i,  the  position  of  the  parts  being  found  by  the  same 
>us  as  that  employed  for  Fig.  121,  and  it  is  seen  that 
the  lead  is  here  also  increased  by  moving  the  link  from 
full  to  mid-gear,  whereas,  in  the  absence  of  the  rocker 
(the  link  having  crossed  rods),  it  would  diminish.     The 


its  center  coincident  with  the  center  of  the  rocker-shaft, 
so  that  the  link  and  the  link-block  would  move  together 
in  the  same  arc  ;  but  as  the  lifting  shaft  arm  moves  in 
an  arc,  therefore,  locating  the  point  of  suspension  for 
full  gear  at  the  center  of  the  rock  shaft  throws  the 
point  of  suspension  for  the  mid  and  backward  gear 
away  from  the  line  a  a,  upon  which  it  would  require  to 
lie  to  enable  the  saddle-pin  and  the  link-block  to  move 
as  nearly  as  possible  in  the  same  arc,  and  thus  mini- 
mize the  amount  of  sliding  motion  of  the  link-block  in 
the  link  slot.  Obviouslyjiie  longer  the  arm  P  of  the 


94 


MODERN  STEAM  ENGINES. 


lifting  shaft,  the  mere  nearly  its  arc  of  motion  (in  lift- 
ing the  link  from  full  gear  forwards  to  full  gear  back- 
yards) will  coincide  with  the  line  a  o,  and  the  more 
perfect  the  suspension  will  be,  or,  in  other  words,  the 
less  the  sliding  motion  of  the  link-block  in  the  link  arc. 
Considerations  of  room,  however,  usually  limit  the 
length  of  P  to  about  half  that  of  the  eccentric-rods, 
and  the  sliding  motion  of  the  link-block  may  be  mini- 


link-hanger  would  move  in  shifting  from  full  gear  for- 
ward to  full  gear  backward.  The  points  of  link-hanger 
suspension  would,  in  this  case,  be  in  the  most  desirable 
positions  for  the  full  gears,  because  they  are  both  on  the 
line  a  a,  causing  the  center  of  the  saddle-pin  to  vibrate 
on  an  arc  as  near  as  possible  parallel  to  the  arc  t  t,  in 
which  the  link-block  moves;  hence  there  would  !«•  a 
minimum  of  sliding  motion  of  the  link-block  in  the 


Fig.   123. 


mized  for  the  full  or  mid-gears  as  follows  :  For  the 
full  gears,  we  take  the  length  of  the  link-hanger  as  a 
radius,  and  from  v' — the  center  of  the  link  when  in  full 
forward  gear — draw  an  arc  TO  somewhere  on  which  the 
upper  end  of  the  link-hanger  will  be  when  the  link  is 
in  full  forward  gear.  "With  the  same  radius,  and  from 
v  as  a  center,  we  mark  arc  I  somewhere  upon  which  the 
upper  end  of  the  link-hanger  will  be  when  the  link  is 
in  mid-gear.  With  the  same  radius,  and  from  v" — the 
center  of  the  link  when  in  full  backward  gear — draw 
an  arc  k,  upon  which  the  upper  end  of  the  link-hanger 
will  be  when  the  link  is  in  full  gear  for  the  backward 
motion.  With  the  length  of  the  lifting-shaft  arm — P, 
Fig.  11G — as  a  radius — and  from  the  points  of  inter- 
section of  arcs  TO  nnd  k  with  the  line  a — find  at  S'  the 
\  position  for  the  center  of  the  lifting-shaft,  from  which 
may  be  drawn  arc  y  y,  on  which  the  upper  end  of  the 


link-slot.  For  the  mid-gear,  we  have  so  located  the 
hanger  suspension  that  the  centers  of  both  the  link- 
block  and  the  saddle-pin  arc  on  the  arc  /  at  r,  but  as  the 
point  of  hanger  suspension  would  be  to  the  right  of  a  a, 
the  saddle-pin  arc  would  vary  from  that  of  the  link- 
block,  and  sliding  motion  would  ensue. 

The  reverse  of  this  would  be  the  case  if  the  center 
of  the  lifting  shaft  were  located  at  the  point  S",  meeting 
the  line  a  at  a  point  coincident  with  the  center  of  the 
rocker-shaft,  for,  in  that  case,  the  motion  of  the  hanger, 
or  of  the  link  and  of  the  link-block,  would  coincide! 
more  nearly  when  the  link  was  in  mid-gear  than  when 
in  full  gear,  and  the  amount  the  block  would  slide  in 
the  link  would  be  lessened  at  mid  and  increased  at  full 
gear. 

By  locating  the  center  of  the  lifting  shaft  at  S,  the 
path  of  the  upper  end  of  the  link-hanger,  when  moving 


/./.YA'  MOTIONS   WITH  ROCK  SHAFT. 


95 


the  link  from  full   gear,  would   be   on    the   full    1 
midway  between   arc-  y  y  and   I    y.  which    pa 

being  as   far   from    that   lino, 

-  when  in  mid-gear,  thus  equal- 

the  amount  of  sliding  motion  of   the  link-block  in 

It  may  now  be  pointed  out  that   the  employme:: 

-  diminishes  the  amount  of  .-liding  motion  of  the 
link-block  in  the  link-slot,   because  the  lower  arm  of   the 

e  link-block  to  move  in  an  arc  of  a  circle 

that  more  .  ucides  with    the   arc   in   which   the 

saddle  pin  moves,    whereas,  in   the  absence  of  a   rocker. 

de  spindi.-   :-   guided  to  move   in   a  straight  line. 

The  link  motion,  having  the  same  proportions  as  in  pro- 

•  •samples,  and  as  given  on  page  i;\  and  the  length 

the   rocker   being   each    12    inches,   the 
••pollings  will  IM>  as  follows  : 
In  Fig.   121.  the  full  liin  •  .vard  full  gear  while 

3 3 


\ 


\ 


1.' 


\ 


\ 


\ 


\ 


V 


/ 


y? 

4as£ 


1-nj.     124. 

•i  ted  lines  represent  the  full  gear  backward,  the 
^ad'lle -pili  being  on  the  lino  of  the  center  of  the  link- 

.•I  the  hanger  suspended  on  the  arc  denoted  by 
the  full  line  in  Fig.  12.'!,  so  as  to  minimize  the  amount 
of  sliding  of  the  link-block  in  the  link,  .and  it  is  seen 

be  events  are  as  nearly  equalized,  as  is  necessary, 
for  the  backward  and  forward  gears.  Thus  when  the 
jii.-ton  moves  from  I?  to  D,  the  cut-off  is  at  19J  inches 
for  the  forward  gear  and  19f  inches  for  the  backward 


,  while  when  it  is  moving  from  I)  to  I!,  the  cut-olT 
is  at  1 9f  inches  [or  both  gears.  Similarly,  the  points 
of  release  and  cushion  are  \<  rj  nearly  eijua,. 


B 


N 


\ 


\ 


S 


\ 


\ 


\ 


s 


x 


s 


\ 


\ 


\ 


\ 


/•'/</.  rj.v 

Tlie  port  openings  for  the  cut-off,  at  half-gear,  arc 
shown  in  Fig.  125,  and  it  is  seen  that  the  events  are  all 
equalized  for  the  backward  and  forward  gears,  but  that 
the  point  of  cut-off  is  an  inch  later  when  the  piston  is 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


/•'/,/.    12fi. 

moving  from  D  to  B  than  when  it  is  moving  from  1> 
to  D. 

Fig.  12G  shows  the  port  openings  for  mid-gear,   the 


9G 


MODERN  STEAM  ENGINES. 


port  only  opening  to  the  amount  of  the  lead,  and 
beginning  to  close  as  soon  as  the  crank  leaves  the 
dead  center.  The  lead  is  here  again  equalized,  and  it 
is  seen,  from  these  three  figures,  that  the  lead  increases 
as  the  link  is  moved  from  full  gear  to  mid -gear.  This. 
however,  may  be  remedied,  for  the  forward  gear, 
at  the  expense  of  the  backward  gear,  by  the  means 
described  for  open  rods,  and  with  reference  to  Figs. 
99  and  100,  the  only  difference  being  that  as  the 
rods  are  in  this  case  crossed,  the  eccentrics  must  be 
set  back  instead  of  being  set  forward,  as  in  the  case  of 
open  rods. 

EQUALIZING    THE    POINTS    OP    CCT-OFF. 

Referring  now  to  the  equalization  of  the  points  of 
cut-off,  it  may  be  effected  in  five  ways,  first  by  giving 
to  the  valve  more  steam  lap  at  the  head  end  than  at 
the  crank  end,  as  has  already  been  explained  in  con- 
nection with  the  subject  of  diagrams  for  designing 
valve  motions,  secured  by  making  the  steam  ports  of 
unequal  widths,  us  will  be  explained  presently;  third  by 
suitably  locating  the  point  of  suspension  of  the  upper 
end  of  the  link  hanger,  or  in  other  words,  suitably 
locating  the  lifting-shaft;  fourth  by  suitably  locating 
the  position  of  the  saddle-pin,  or  in  other  words,  by 
setting  it,  back  towards  the  eccentric-rod  eye,  instead 


Fig  127,  for  example,  is  a  diagram  of  the  port  open- 
ings, the  arc  of  hanger  suspension  having  been  moved 
back  three  inches,  and  corresponding  with  arc  Z  Z  in 
Fig.  123,  (supposing  that  arc  to  be  distant  3  inches 
from  the  middle  or  full  line  arc  of  hanger  suspension 
shown  in  that  figure.)  If  we  compare  Fisr.  128  with 
Fig.  12"),  we  find  that  the  equalization  of  the  points 
of  cut-off  has  been  accomplished  at  the  expense  of  the 
port  opening,  because  while  we  have  caused  the  cut-off 
to  occur  an  inch  earlier  on  the  stroke  from  D  to  B,  we 
have  reduced  the  port  opening  for  that  stroke.  The 
arc  of  hanger  suspension  being  moved  another  three 
inches  back,  the  port  openings  will  be  as  in  Fig.  12S, 
and  it  is  seen,  that  although  the  points  of  cut-off  are 
still  equalized,  the  port  openings  are  widely  distorted, 
which  is  a  serious  defect.  It  is  suen,  therefore,  that  the 
points  of  hanger  suspension  may  lie  located  consider- 
ably to  the  left  of  the  line  n  n.  without  much  influence 
on  the  points  of  cut-off. 

The  cause  of  the  equalization  of  the  points  of  cut-off 
and  reduction  of  port  opening  by  means  of  the  points 
of  suspension,  may  be  seen  from  Figs.  129  and  130,  in 
which  the  parts  are  shown  in  the  positions  they  occupy 
at  the  point  of  cut-oil  when  that  point  is  at  half  stroke, 
b  b  is  the  line  of  centers  of  the  engine  I  I,  the  arc  in 
which  the  link  block  moves,  and  P  the  path  of  saddle- 
pin  motion,  while  ,r  x  is  an  imaginary  line  parallel  to 


f 

—  •* 

•  —  , 

~~s 

X 

^-" 

^- 

-—  - 

^ 

~~- 

•^ 

N 

^ 

^ 

* 

*> 

^ 

s 

- 

^ 

' 

^— 

N 

B 

> 

\ 

/ 

/ 

S 

D 

B 

\ 

\, 

\ 

^ 

/ 

' 

' 

I) 

of  having  it  on  a  line  with  the  center-line  of  the  arc  of 
the  link-slot,  and  fifth,  by  lifting  the  link  to  diff- 
erent amounts  for  corresponing  points  of  cut-off  for  the 
two  gears,  but  in  proportion  as  we  set  either  the  points 
of  hanger  suspension,  or  the  saddle  pin  back,  we  decrease 
the  amount  of  port  opening,  especially  at  the  head  end 
of  the  c'vlinder. 


Fig.   128. 

line  I  I,  and  inserted  merely  to  compare  the  arc  P  with. 
It  is  seen  here  that  the  saddle-pin  is  (on  account  of 
moving  on  the  arc  P)  lifted  up  towards  the  line  of 
centers  I  I,  and  this  lifting  obviously,  from  the  position 
of  the  link  in  Fig.  129,  moves  the  lower  arm  of  the 
rocker  to  the  right  and  the  upper  arm  to  the  left,  thus 
hastening  the  point  of  cut-off  ;  this,  however,  is  obvi- 


7./.VA' 


NS    \\TJ-Ji    i:i.X'K    .S7/.1/-T. 


97 


nted  by  locating  the  point  of  .suspension  lower  down  on 
the  arc  /,  fixing  its  position  so  ihiit  the  cut-oil  will,  on 
iroke    represented    in    Fig.    129,    occur   at  half 
stroke. 

\Vo  Lave  now  to  consider  the  return  stroke,  Fig.  130, 


ing  the  point  of  cut-off  on  the  stroke  from  D  to  B.  and 
equalizing  the  points  of    cut-off   for  the  two   stro! 

THE    EFFECT    OF    OIVINCJ    THE    VALVE    OVEKTRAVEL. 

Iii  the  previous  examples,  the  travel  of  the  valve  has 


i 


\ 


.Fty.   129. 


and  it  is  here  again  seen  that  setting  the  arc  Z  back  has 
caused  the  link  to  lift  on  the  arc  P,  and  this  lifting  has, 
on  account  of  the  position  the  link  hangs  in,  moved  the 


been  4£  inches,  so  that  the  steam  edge  of  the  valve 
traveled  but  £  inch  more  than  the  amount  necessary  to 
fully  open  the  steam  port.  It  is  customary  in  Ameri- 


130. 


r  rocker-arm   to  the  left  and  therefore  the  upper    can  locomotive  practice,  however,  to  give  to  the  valve 
rocker-arm  and  the  valve  to  the  right,  and  so  hasten-     from  f  inch  to  f  inch  of  overtravel.     Leaving  the  ports 


98 


MODERN  STEAM  ENGINES. 


I  ^  inches  and  the  steam  lap  at  -J-  inch,  as  in  our  former 
examples,  wo  may,  therefore,  now  increase  the  travel  of 
the  valve  to  5§  inches,  giving  Jj-  incli  overtravel. 

The  port  openings  in  full  gear  will  now  be  as  in  Fig. 
131,  and  it  will  be  seen,  on  a  comparison  with  Fig.  88, 
that  the  admission  has  been  hastened,  and  the  points  of 
cut-off  delayed,  reducing  the  amount  of  expansion. 
Furthermore,  the  exhaust  opening  has  been  reduced  by 
the  reclosure  from  a  to  b  and  from  c  to  d,  which  occurs 
because  of  the  valve  partly  closing  the  cylinder  exhaust 
port,  as  seen  in  Fig.  13'2,  at  e,  the  overtravel  of  the 
valve  being  shown  at  x.  This  may  obviously  be  reme- 
died by  widening  the  bridges  and  correspondingly 
widening  the  valve. 

The  overtravel  of  the  valve  has  no  effect  upon  the 
port  openings  at  shorter  points  of  cut-off,  which  will 
remain  the  same  as  if  there  were  no  overtravel  at  full 
gear.  But  the  overtravel  will  render  it  necessary  to 
lift  the  link  more  in  order  to  effect  the  cut-off  at  a 
given  point,  thus  bringing  the  link-block,  for  any  given 
point  of  cut-off  (less  than  full  gear),  nearer  to  the  center 
of  the  link,  and  thus  slightly  diminish  the  amount  of 
sliding  motion  of  the  block  in  the  link. 

EQUALIZING  THE  POINT  OF    CUT-OFF    BY    MAKING    THE  STEAM 
FORTS  OF    DIFFERENT  WIDTHS. 

It  may  now  be  pointed  out  that  the  points  of  cut-off 
may  be  equalized  by  making  the  steam  ports  of  differ- 
ent widths. 

In  Fig.  133,  for  example,  we  have  the  parts  drawn 
one-eighth  full  size,  the  outer  circle  representing  the 
path  of  the  crank,  and  the  circle  n  representing  the  path 
of  the  eccentric.  The  smallest  circle  has  a  radius  equal 
to  the  amount  of  steam  lap,  which  is  equal  for  both 
ports. 

The  connecting-rod  has  the  usual  proportion  of  three 
times  the  length  of  the  piston  stroke,  which  is,  in  this 
example,  24  inches ;  hence  the  connecting-rod  is  72 
inches.  The  width  of  steam  port  is  1^  inches,  the  steam 
lap  $  inches  and  the  valve  travel  4£  inches,  the  latter 
being  just  enough  to  fully  open  both  ports  for  the  ad- 
mission. 

With  these  dimensions,  it  may  be  found  by  means  of 
Zeuner's  diagram  (which  has  already  been  fully  ex- 
plained in  Chapter  II)  that  the  point  of  cut-off  for  the 


port  at  the  head  end  will  occur  at  20  inches  of  piston 
stroke,  while  that  for  the  port  at  the  crank  will  occur 
at  the  nineteenth  inch. 

Let  it  be  supposed  that  the  points  of  cut-off  are  to 
be  equalized  at  20  inches,  and  we  proceed  as  follows  : 

In   Fig.  133    we  draw,    from  a   center   0,  the   outer 


S" 


\ 


\ 


\ 


\ 


\ 


Fig.   131. 

circle  representing  the  path  of  the  crank-pin,  and  a 
circle  n  representing  the  path  of  the  eccentric  center, 
the  inner  circle  d  having  a  radius  equal  to  the  amount 
of  steam  lap.  From  the  edge  of  circle  d,  we  draw  a 


vertical  line  ?,  and  a  line  from  C,  cutting  the  inter- 
section of  e  with  circle  it.  gives  the  position  of  the  eccen- 
tric at  the  point  of  cut-off,  the  crank-pin  being  at  S. 

We  may  now  draw  the  ports  and  the  valve  in  posi- 
tion to  effect  the  cut-off.  We  have  now  to  find  how 
much  to  cut  out  the  port  at  the  crank  end  in  order  to 


THE     CUT-OFF. 
Fig.   133. 


99 


UNI'V          SITY, 


s  v 


\>.  134. 


cause  the  cut-off  to  occur  at  the  twentieth  inch  instead 
ot  at  the  nineteenth,  and  this  may  be  done  as  follows  : 
In  Fig.  134,  arc  r  represents  the  position  the  piston 


must  be  in  when  the  cut-off  occurs  (being  the  same 
distance  from  B  that  s  is  from  D).  From  the  lap  circle 
d,  we  drop  a  perpendicular  line  u,  and  a  line  from  C 


100 


MODERN  STEAM  ENGINES. 


passing  through  the  point  of  intersection  of  u  with 
circle  n,  gives  us  the  position  of  the  eccentric  when  the 
cut-off  will  occur,  if  the  port  a  is  made  the  same  width 
as  port  b.  By  prolonging  the  eccentric  throw-line  to  v, 
we  are  enabled  to  find  the  crank  position  by  taking  the 
radius  S  V  (Fig.  133),  and  marking  from  i>,  in  Fig.  134, 
an  arc  in.  A  line  drawn  from  the  point  of  intersection 
of  TO  with  the  outer  circle  to  the  center  represents  the 
throw-line  of  the  crunk.  We  have  thus  found  the  posi- 
tions of  the  crank  and  of  the  eccentric  when  the  cut-oil 
will  occur,  the  ports  being  of  equal  width,  and  we  may 
now  find  the  positions  they  ought  to  be  in  in  order  to 
equalize  the  points  of  cut-off.  To  do  this,  we  draw 
from  the  arc  r,  and  with  the  length  of  the  connecting- 
rod  as  a  radius  (this  length  being  represented  by  three 
times  the  diameter  of  the  outer  circle),  the  arc  w,  giving 
us  at  H  the  position  the  crank  ought  to  have  arrived  at 
when  the  cut-off  occurred,  and  we  find  that,  as  the  cut- 
off occurred  when  the  crank  was  at  h  and  the  eccentric 
at  v,  it  occurred  too  early  in  the  stroke,  because  the 
crank  ought  to  have  arrived  at  II.  Now,  suppose  it  to 
have  reached  position  H,  and  we  may  find  the  corres- 
ponding eccentric  position  by  taking  the  radius  h  v 
and  marking  from  II  an  arc  x,  giving  us  the  required 
eccentric  position  at  y. 

To  find  the  difference  in  the  positions  of  the  valve 
when  the  eccentric  is  in  the  positions  denoted  by  v  and 
x  respectively,  we  draw  from  the  point  of  intersection 
of  line  v  with  the  circle  n  a  perpendicular  line  u,  and 
from  u  point  of  intersection  of  line  x  with  the  circle  n, 
a  vertical  line  y,  and  the  distance,  measured  on  the  line 
of  centers  1  1,  between  these  two  vertical  lines,  is  the 
amount  the  valve  will  have  traveled  past  the  steam  edge 
of  the  port. 

Now,  suppose  we  cut  out  the  port  a  to  the  dotted  line 
/,  and  it  is  seen  that  the  crank  will  be  at  H,  the  eccen- 
tric at  y,  and  the  cut-off  just  effected,  the  piston  being 
at  r  and  the  points  of  cut-off  equalized  by  cutting  out 
port  a  to  line/. 

Let  it  be  supposed  that  it  is  determined  to  equalize 
the  points  of  cut-off  by  altering  the  width  of  port 
b,  or  in  other  words,  on  the  stroke  when  the  piston  is 
moving  from  the  head  end  D  to  the  crank  end  B  of  the 
cylinder,  then  it  is  necessary  to  proceed  as  follows  : 

In  Fig.  135,  noint  >•  is  located   to  represent  the  nine- 


teenth inch  of  piston  motion  from  B,  and  an  arc  w  gives 
at  II  the  crank  position  at  the  time  the  cut-off  occurs. 
A  vertical  line  e,  touching  the  lap  circle  d,  gives,  at  its 
intersection  with  the  eccentric  path  n,  the  throw-line  V 
of  the  eccentric,  which  is  prolonged  to  v  in  order  to 
get  on  the  outer  circle  the  position  the  eccentric  will  1  ;e 
in  when  the  crank  is  at  H.  Having  found  the  positions 
of  the  crank  and  eccentric  at  the  time  of  cut  off,  we 
may  draw  in  the  valve,  the  cut-off  at  port  a  being  jiut 
effected.  For  the  other  stroke  we  proceed  as  in  Fig. 
1 .'!(!,  in  which  the  circles  correspond  to  tkose  in  Fig. 
11)5,  the  arc  s  being  the  same  distance  from  D  that  /  is 
from  B  in  Fig.  135,  and  therefore  representing  the 
piston  position  for  equalized  points  of  cut-off. 

With  a  radius  equal  to  three  times  the  diameter  of 
the  quter  circle  E,  and  from  a  point  on  the  line  of  centers 
/  /.  we  mark,  from  .?,  an  arc,  giving  us  at  II'  the  crank 
position  at  the  time  of  equalized  cut-off. 

To  find  the  corresponding  eccentric  position,  we  take 
the  angle  the  eccentric  stands  at  to  the  crank  or  radius 
h  r,  Fig.  135,  and  mark,  from  II',  Fig.  130,  an  arc,'/, 
and  from  where  <j  cuts  the  outer  circle  draw  a  line  z 
giving  us  the  eccentric  position  corresponding  to  crank 
position  H. 

.But  by  drawing  a  vertical  line  u  from  the  lap  circle 
and  a  line  C  c,  we  find  that  the  cut-off  will .  not  occur 
tmtil  the  eccentric  throw  has  reached  the  line  C  c,  which 
will  be  too  late  to  give  an  equalized  cut-off,  because 
when  the  eccentric  has  arrived  at  c,  the  crank  will 
be  at  H"  instead  of  at  H'  as  may  be  proved,  because 
radius  H'  g  equals  radius  H"  c. 

In  the  figure,  the  valve  is  drawn  in  the  position  it 
would  occupy  when  the  crank  was  in  its  proper  position 
H'.  the  port  b  being  still  open,  and  it  becomes  clear  that, 
in  order  to  equalize  the  point  of  cut-off,  we  may  make 
the  port  b  narrower,  bringing  its  steam  edge  on  the 
line  p. 

The  amount  to  which  we  must  decrease  its  width  may 
be  found  by  dropping  a  perpendicular  line  y  from  the 
point  of  intersection  of  line  x  with  circle  n,  and  meas- 
uring the  distance  between  lines  u  and  y.  It  is  obvious 
that  it  is  preferable  to  draw  the  outer  circle  to  a  diame- 
ter equal  to  the  full  travel  of  the  valve,  and  let  it  rep- 
resent the  crank  path  on  a  reduced  scale,  as  the  lines 
will  be  clearer,  and  correctness  may  more  easily  be  ob- 


zixi;  THI-:  CUT-OFF. 

i<j.   135. 


101 


>.  136. 


tained.  Equalizing  the  points  of  cut-off,  by  thus 
making  the  ports  of  different  widths,  possesses  the 
advantage  that  the  laps  of  the  valve  are  maintained 


equal,  and  the  valve  may  be  put  on  end  for  end  with- 
out being  put  on  wrong,  which  might  occur  if  the  laps, 
instead  of  the  ports,  were  made  of  unequal  widths. 


UODERX  STEAM  ENGINES. 


MODIFIED    FORMS    OF    LINK    MOTION    REVERSING    OEAIiS. 

A  link  motion,  in  \vhich  but  one  eccentric  is  em- 
[  .'loved,  is  sho\vn  in  Fig.  137,  which  is  taken  from  The 
American  MacJiiiiint.  The  saddle-pin  is  on  the  lino  of 
centers  A  and  remains  there,  the  link-Llock  being 
moved  along  the  link-slot  to  vary  the  point  of  cut-off, 
or  reverse  the  direction  of  motion,  as  in  Gooch's  link 
motion.  On  the  rod  E  that  connects  the  link-block  and 
slide  spindle,  there  is  provided  a  latch  F  (on  the  end  of 
rod  D)  which,  in  conjunction  with  the  notches  on  the 
concave  side  of  the  link,  holds  the  link  in  its  adjusted 
position.  In  this  arrangement,  there  is  the  objection 
that  when  the  link-block  and  rod  E  are  at  the  same  end 
of  the  link  as  the  eccentric-rod,  the  weight  of  both  E 
and  the  eccentric  rod  is  borne  by  the  eccentric. 

In  the  Stephenson's  link  .motion,  shown  in  Fig.  78, 
and  the  Gooch's  link  motion  shown  in  Fig.  114,  the 
lifting-shaft  is  shown  above  the  'link,  but  it  is  often 
more  convenient,  from  the  construction  of  the  engine, 
to  place  it  below  the  link,  as  in  Figs.  138  and  139, 
which  are  from  Mechanics.  This  plan  is  common 
upon  engines  for  hoisting  purposes. 

STEAM    REVERSING    GEARS. 

In  cases  where  the  power  required  to  move  the  link 
motion  is  more  than  can  be  exerted  by  hand,  a  special 
steam  cylinder  is  employed  to  assist  in  moving  the 
reversing  shaft,  examples  of  this  kind  being  given  in 
Figs.  140  and  141,  which  are  from  Mechanics.  In  Fig. 
140,  A  is  a  steam  cylinder,  with  ports,  slide-valve,  steam 
chest,  &c.,  of  the  ordinary  construction.  C  is  the  main 
reversing  lever,  the  bottom  end  of  which  is  keyed  to 
the  tumbling  shaft;  its  upper  end  projects  a  few  inches 
above  the  quadrant,  and  is  provided  with  a  detent  for 
latching  it  to  the  quadrant.  The  connecting-rod  II,  of 
the  stearn  cylinder,  is  attached  to  this  lever  at  B.  D  is 
the  hand  lever,  having  its  fulcrum  at  1  on  the  main 
lever.  Its  upper  end  has  a  handle  and  thumb  latch,  of 
the  ordinary  construction,  attached  by  a  rod  to  the 
detent  on  the  main  lever.  When  the  hand  lever  is  in 
the  central  position,  the  pin  at  its  lower  end  coincides 
witii  the  a.xis  of 'the  tumbling  shaft  (if  the  gear  is  not 
at  the  end  of  the  tumbling  shaft,  the  shaft  will  require 
to  be  cranked  to  allow  for  this).  On  the  main  lever,  at 


K,  are  stops  which  limit  the  motion  of  the  hand  lever 
to  the  travel  of  the  valve.     The  lower  end   of  the  hand 


Fig.  137. 

lever  is  connected  by  links  and  levers  to  the  valve-stem, 
as  shown.     The  weight  of  the  links,  &c.,  is  balanced  by 


.v 77-:.  i  M  i;  /•:  \ ' /-.v/.v/  NO   <>'  /•:.  i  RS, 


103 


n  weight  in  the  usual  way.     Tin-  engineer  unlatches  the 

•  hand  lever  in  tin-  direction  he  v. 
,  t!:<i   lever  moves   until  its  lower  e:id 
p   K.     The   steam   valve   is   then   in   the   ; 
in  t«-  admit  steam  to  the  cylinder  A,  and  its  piston 
him  to  move    the  lever.      When    ho    wishes    to 


screw  can  l>e  arranged  at  E  with  two  nuts,  and  used  for 
regulating  the  amount  of  the  travel  of  the  p!s:on.  a;:<l 
thus  effecting  the  cut-off  in  the  cylinder  by  changing 
the  travel  of  the  main  valve.  This  makes  a  very  satis- 
fy gear  for  reversing  on  a  reversible  rolling-mill 
engine.  For  hoisting  purposes,  where  great  delicacy  is 


Fig.   138. 


reverse,  he  pushes  the  hand  lever  in  the  opposite  direc- 
tion, which  changes  the  position  of  the  valve  and  re- 
le  operation.  He  can  thus  move  the  lever  and 
l.itch  it  at  any  point  of  the  quadrant.  In  Fig.  141,  the 
hand  lever  is  dispensed  with,  the  steam  piston  being 
attached  directly  to  the  reversing  lever.  A  is  the 


required,  it  is  open  to  the  objection  that  it  has  nothing 
positive  by  which  the  load  may  be  stopped  at  a  fixed 
point.  This  arrangement  may  be  modified  by  the  addi- 
tion of  a  cataract  as  shown  in  Fig.  142,  in  which  A  is 
the  steam  cylinder  and  B  a  hollow  piston,  having  an 
arm  C,  for  carrying  the  rod  D,  on  which  is  the  cataract 


Fig.    139. 


reversing  cylinder,  B  the  valve  chest,  C  the  small  lever 
for  moving  the  valve,  and  D  D  the  rods  connecting  to 
the  links.  There  is  a  valve  on  the  exhaust  pipe  of  this 
small  cylinder,  which  is  used  for  regulating  the  rapidity 
of  the  motion  of  the  piston.  A  right  and  left  hand 


piston  E;  at  P,  is  the  rod  for  the  valve  that  admits 
steam  to  A,  and  at  G  is  the  piston  rod  that  attaches  to 
the  lifting-shaft  arm.  H  H  is  a  pipe  having  communi- 
cation with  each  end  of  the  cataract  cylinder,  which  is 
filled,  on  each  side  of  tin;  piston  K,  with  water  or  oil. 


UNIVERSITY 


104 


MODERN  STEAM  ENG1XES. 


Now  suppose  that  steam  is  admitted  to  cylinder  A,  and 
it  is  clear,  that  if  cock  J  of  the  cataract  pipe  is  closed, 
the  piston  in  A  cannot  move,  because  it  is  connected, 
through  its  rod  and  the  arm  C,  to  the  cataract  piston 


until,  by  passing  beneath  the  auxiliary  valve,  its  ports 
are  again  closed,  when  motion  will  close,  because  the 
steam  can  neither  enter  nor  exhaust  from  the  cylinder, 
hence  the  motion  of  the  piston  follows  that  of  the  hand 


Fig.    140. 


E.  But  if  we  open  the  Cock  J,  then  the  parts  will 
will  move,  the  water,  on  one  side  of  piston  E,  passing 
through  pipe  II  to  the  other  side  of  E.  The  speed 
with  which  motion  will  ensue,  obviously  depends  upon 
how  widely  cock  J  is  opened,  or  in  other  words,  upon 
how  fast  the  water  can  pass  from  one  to  the  other  side 
of  piston"  E.  By  regulating  the  amount  of  opening  of 
cock  J,  therefore,  the  motion  of  the  steam  piston  in 
cylinder  A,  may  be  made  as  slow  as  desired,  enabling 
the  engineer  to  shut  off  steam  to  A,  and  thus  arrest  the 
motion  of  the  reversing  gear,  at  any  acquired  point  with 
great  precision.  The  cataract  cylinder,  may  obviously 
be  placed  at  the  end  of  the  steam  cylinder,  as  shown  in 
Fig.  143,  in  which  case  one  piston  rod  serves  for  both 
the  steam  and  the  cataract  pistons.  Fig.  144,  (from 
Mechanics),  represents  a  form,  in  which  an  auxiliary 
valve  is  employed,  the  main  valve  connecting  to  the 
lifting  shaft  at  B,  while  the  auxiliary  valve  is  operated 
by  a  hand  lever. 

]n  this  arrangement  the  hand  lever  may  be  operated 
to  open  the  ports  in  the  main  valve,  which  will  move 


lever,  and  when  the  link  motion  has  moved  to  the  re- 


Fig.   141. 


.v  •/•/•:.  i  M  it  /•:  i '  /-.7/.S7  .v  o   G  /•:.  i  /.-x. 


105 


B 


.   143. 


position,  the  lever  handle  may  be  released  and 
will  remain  at  rest. 

Figs.  1  15  and  146  represent  a  steam  reversing  gear. 
-,'iied  by  Mr.  ~W.  E.  Good,  and  employed  on  loco- 
motives on  the  Philadelphia  uml  Heading  Railroad.  In 
l'ig.  ll.'i.  the  gear  ia shown  in  position  on  the  engine. 
while  in  Fig.  146,  it  is  shown  detached  with  the  cylin- 
der in  section.  If  tiiis  gear  is  simply  started,  it  will 
continue  its  movement  in  the  same  direction  until,  by 
dropping  the,  latch  into  the  quadrant  notch  at  the  do- 


Fig.   144. 

sired  point  of  Cut-off,  further  movement  is  arrested. 
The  link  gear  of  the  engine  is  simultaneously  adjusted 
to  the  position  corresponding  with  that  of  the  reverse 
lever.  It  remains  fixed  in  that  position  until  further 
change  is  made  by  the  reverse  lever. 

From  this  general  statement,  it  will  be  seen  that  not 
only  is  the  link  or  other  gear  of  the  engine  moved  by 
the  steam  reverse,  but  also  that  the  reverse  lever  has 
communicated  to  it,  by  the  peculiar  arrangement  of 


106 


MODERN  STEAM  ENGINES. 


the  reverse  gear,  the  necessary  force  to  move  it  to  any 
desired  direction,  without  any  effort  on  the  part  of  the 
engineer,  save  that  of  starting  it.  In  Fig.  14G,  A  is  a 
steam  cylinder,  and  B  the  piston  whose  rod  C  is  guided 
by  two  glands,  which  are  screwed  up  somewhai  tightly. 
C  is  attached  to  the  arm  D  of  the  reverse  shaft.  E  is 
the  steam  valve  operated  by  the  rod  E2,  which  is  pivo- 
ted at  FI  to  the  lever  F.  The  arm  D2  F2  connects  D 
to  F,  and  the  rod  G  connects  the  handle  H  to  F  at  the 
point  F3.  The  valve  E  covers  the  steam  ports  by  about 


rest.  The  link  is  held  by  friction  on  the  piston  rod  C. 
If,  for  any  reason,  the  piston  B  should  begin  to  creep, 
its  rod  would  move  the  rod  D  at  C2.  the  motion  being 
increased  by  D2  by  reason  of  the  increased  length  of 
leverage.  This  increased  motion  would  be  conveyed  to 
F,  which  would  operate  on  its  pivot  F3,  moving  F> 
and,  therefore,  &  to  the  left.  E2  would  move  the 
valve  E  so  as  to  admit  steam  through  the  passage  n'  to 
the  side  b  of  the  piston.  The  piston  would,  therefore, 
be  resisted  by  the  steam  pressure,  and  would  be  held 


Fig.   145. 


^  of  an  inch.  The  gear  is  shown  in  the  full  lines  as 
being  in  mid-position.  If  the  lever  H  is  moved  to  the 
right,  it  will,  through  G,  move  F  on  F2  as  a  pivot,  and 
give  end  motion  to  the  rod  E8,  and  by  this  means  to 
the  valve  E,  admitting  steam  through  the  passage  way 
a,  and  moving  13  in  the  same  direction  as  the  handle  H 
is  moved.  At  the  same  time,  the  link  will  be  lowered. 
When  H  is  brought  to  a  stop,  the  arm  F  operates  on 
its  pivot  F3,  and  as  D  continues  to  move  to  the  right, 
it  moves  F2  to  the  right  and  F1  tcf  the  left,  so  that  the 
rod  E2  closes  the  valve  E,  and  the  piston  B  comes  to 


stationary  by  it.  Since  there  is  but  -£%  inch  lap  on  the 
valve  E,  it  will  be  seen  that  the  increased  motion  at  D*, 
over  that  at  C2,  will  cause  steam  to  be  admitted  through 
a'  with  a  very  small  amount  of  piston  motion.  This 
amount  may  be  regulated  at  will  by  increasing  the 
height  of  D2  above  C2. 

It  will  be  observed,  therefore,  that  this  apparatus 
embodies  a  very  simple  and  ingenious  motion.  The 
action  of  the  parts  centering  on  the  fact  that  moving 
H  forward  causes  F1,  Es,  E  and  therefore  B,  to  move 
in  the  same  direction.  On  the  other  hand,  if  motion 


STEAM  at-: vr.n^ixc  GEARS. 


107 


begins  at  B  instead  of  at  II,  then  F1,  Es  and  E  m<>\v  j  suits  are  obtained  in  whatever  direction  or  to  whatever 

I-'i'j.    UG. 


m  the  opposite  direction,  causing  steam  to  enter  and 
check  the  motion  of  B.     It  is  obvious  that  the  same  re- 


amount  H  is  moved,  and  that  the  checking  or  detaining 
action  is  entirely  automatic. 


14 


CHAPTER    V. 


ADJUSTABLE  CUT-OFF  ENGINES. 


When  a  separate  valve  is  employed  to  effect  the  cut- 
off, and  the  cut-off  valve  is  set  to  operate  at  some 
fixed  point  in  the  piston  stroke,  this  point  being  varied 
by  altering  the  position  of  the  valve  by  hand,  the 
engine  is  called  an  adjustable  cut-off  engine.  The 
construction  of  such  an  engine  is  shown  in  Fig.  147, 
which  represents  a  design  by  the  Lane  &  Bodley  Co. 
The  main  shaft,  driving  shaft,  or  crank  shaft,  is 
furnished  with  two  eccentrics,  the  inner  of  which 
(whose  rod  is  shown  at  A,  in  the  figure)  operates  the 
main  valve,  while  the  outer  (whose  rod  is  shown  at 
B),  operates  the  cut-off  valve,  c  is  the  guide  for  the 
main,  and  d,  that  for  the  cut-off  valve  spindle.  The 
hand  wheel  at  E,  is  for  operating  a  screw,  which  moves 
the  cut-off  valve  so  as  to  cause  it  to  cut  off  at  the 
required  point  in  the  stroke,  there  being  at  F  an  index, 
to  enable  the  cut-off  to  be  set  at  the  required  point. 
Representatives  of  various  kinds  of  cut-off  valves  are 
given  as  follows: 

Fig.  148  represents  the  arrangement  of  what  is  called 
Meyer's  cut-off.  The  main  valve  rides  upon  the  seat  in 
the  same  position  as  the  common  slide  valve,  hitherto 
treated  of,  the  ports  in  the  cylinder  remaining  the  same 
as  for  a  common  slide  valve.  The  main  valve,  however, 
is  provided  with  ports  or  openings.  K  and  L,  through 
which  the  steam  passes  to  the  cylinder  ports.  Upon 
108 


tin;  back  of  the  main  valve  slide  two  cut-off  valves,  so 
called  because  their  sole  office  is  to  cut  off  the  steam  by 
closing  the  ports  K  and  L,  leaving  the  points  of  admis- 
sion, the  amount  of  valve  lead,  tiie  exhaust  and  the 
compression  to  be  governed  by  the  main  valve,  whose 
action,  so  far  as  these  events  are  concerned,  is  effected 
precisely  the  same  as  it  would  be  by  a  common  slide 
valve  having  the  same  la]  s  and  angular  position  of 
eccentric.  This  will  be  seen  from  the  lower  half  of 
Fig.  148,  in  which  a  common  slide  valve  is  shown  in 
place  of  the  main  valve,  and  it  is  apparent  that  the  edge 
h  of  the  cut-off  valve  will  cut  off  the  steam  the  same 
as  edge  h  of  the  common  slide  valve,  and,  also,  that  the 
edges  J  of  the  two  valves  would  cut  off  alike  if  their  ec- 
centrics occupied  the  same  positions.  It  is  also  apparent 
that  when  edge  h  of  the  main  valve  has  closed  the  port 

_  l>,  the  expansion  will  begin,  independent  of  any  action 
of  the  cut-off  valve.  The  longest  distance  the  steam 
can  be  allowed  to  follow  the  piston  is,  therefore,  gov- 

.  erned  by  the  main  valve,  the  action  of  the  cut-off  valves 
being  confined  to  effecting  the  cut-off  at  some  earliei 
point  in  the  stroke.  This  it  effects  for  one  stroke  by  the 
edge  (r  of  the  cut-off  valve  passing  over  the  edge  </  of 
port  L,  and  for  the  other  stroke  by  the  edge  M,  passing 
over  edge  N  of  the  port  K.  The  point  in  the  piston 
stroke,  at  which  these  two  events  will  occur,  depend 


(UN: 


\ 


" 


109 


110 


M  o  i>  i-:it 


upon  tlie  distance  that  G  stands  from  g,  and  M  from  N, 
if  both  the  valves  were  at  mid-travel,  as  shown  in 
tlio  figure.  To  regulate  this  distance,  so  as  to  effect  the 
cut-off  at  different  points  in  the  piston  stroke  to  suit  the 
amount  of  power  the  engine  may  be  required  to 
possess,  the  cut-off  valves  are  provided  with  nuts  P, 
which  are  a  sliding  fit,  in  pockets  in  the  backs  of  the 
valve,  and  through  these  nuts  passes  a  right  and  left 


desirable  point,  and  incapable  of  moving  from  that 
point.  But  if  the  amount  of  work  performed  by  the 
engine  varies,  or  when  the  steam  pressure  varies,  the 
screw  affords  means  of  either  varying  or  maintaining 
the  power  of  the  engine  by  moving  the  cut-off  valves 
to  alter  the  point  at  which  live  steam  will  be  cut-off. 

In  Fig.  148,  the  main  and  cut-off  valves  are  shown 
in   the  positions   most  convenient  for  explaining  their 


CUT  OFF 


Fig.    148. 


hand  screw  S,  which,  on  being  revolved,  moves  the 
valves,  either  lessening  the  distance  G  g  and  M  N,  or 
increasing  it,  according  to  the  direction  in  which  S  is 
revolved. 

The  object  of  providing  the  cut-off  valves  with  the 
nuts  P,  is  to  permit  them  to  seat  themselves  on  the 
main  valve  (notwithstanding  their  wear)  without  bend- 
ing the  screw  S. 

If  the  work  performed  by  the  engine  was  constant 
in  amount  and  the  steam  pressure  was  also  constant, 
the  cut-off  valves  might-  be  kept  in  one  position  on  the 
screw,  being  adjusted  to  cut  off  the  steam  at  the  most 


construction,  and  not  in  that  in  which  they  would  stand 
when  properly  set  upon  the  engine. 

Suppose  the  cylinder  steam  ports,  and  the  ports  in 
the  main  valve,  to  be  an  inch  wide  and  the  main  valve 
to  have  an  amount  of  steam  lap  equal  to  half  the  width 
of  the  cylinder  steam  ports,  or  in  other  words,  -£  inch 
of  steam  lap,  which  will  give  a  cut-off  at  about  -fa  piston 
stroke,  and  the  travel  of  the  main  valve  being  just  suffi 
cient  to  fully  open  the  steam  ports  the  action  of  tho 
main  valve  will  not  be  unduly  distorted  by  excessive 
lap  nor  over  valve  travel. 

Suppose  the  outer  edges  of  the  cut-off  valve,  if  placed 


RIDING    OUT-OFF    VALVES. 


Ill 


in  mid-p-'sition  on  the  main  valve,  as  in  Kit;.   1  l~ 

distant  In 'in  tho  nearest  edges  of  the  main  valve  ports 
<  an  amount  equal  to  half  the  width  of  the  cylin- 
•,-im  port,  and  the-.-  fcVOMge 

conditions,  we  may   follow  the   movements  of  the  parts 

as  follows  • 


Fig.  l"'l  shows  die  positions  of  the  valves  at  the 
point  of  release  or  exhaust  for  the  port  a,  thus  com- 
pleting the  events  for  one  piston  stroke.  In  moving 
across  the  port  to  effect  the  cut-off,  the  cut-off  valve 
reduces  the  effective  width  of  steam  port  opening,  and 
it  is  neiv.v-ary  to  take  this  into  account  in  considering 


7-P^ 
Z_z_ 


\^       \ 


t'i<j.  14  a. 


In  Fig-  1  10.  the  crank  is  on  its  dead  center  a1  the 
crank  end  H,  tho  cut-off  eccentric   being,  in  this  exam- 
art  ly    opposite  to  the  crank,  and   the  main 
valve  having   no  lead.      It  is   here  seen  that,  the  valves 
moving  in    tlie   direeti.m   denoted  by   their   respective 
arrows,  the  admission  of  the  steam  will  occur  through 
1C  and  a,  uninfluenced  by  the  cut-off  valve. 


the  steam  admission.  In  Fig.  152,  for  example,  it  is 
Ken  that,  although  the  main  valve  steam  port  K  is  full 
open  to  the  cylinder  port  a,  yet  the  effective  width  of 
port  opening  for  steam  admission  is  the  amount  the 
cut-off  valve  leaves  the  port  K  open. 

"We  .may    clearly  perceive  the  action   of    a  cut-off 
valve  .having  the  proportions  already  given,  by  means 


Fig.   150. 


Fig.  150  shows  the  position  of  the  crank,  the  eccen- 
nd  the  valves  when  the  cut-off  occurs,  the  crank 

being  at  half-stroke,  and  it  is  seen  that  the  cut-off  is 
d  by  the  cut-off  valve  independent  of  the  main 

valve. 


of  the  diagram,  in  Fi£.  153,  in  which  lines  A  A  and 
B  B  are  an  inch  apart,  that  being,  in  this  case,  the  width 
of  the  steam  port,  the  lengths  of  these  lines  is  2-J 
inches,  representing,  on  a  scale  of  one-eighth  full  size. 
a  piston  stroke  of  20  inches,  hence  each  of  the  vertical 


112 


MODERN  STEAM  ENGINES. 


lines  indicate  a  piston  stroke  of  one  inch.  The  piston 
being  moved  one  inch,  the  width  of  steam  port  opcn- 
iirj;  is  measured  and  found  to  be  (on  an  engine  having 
a  connecting-rod  whose  length  equals  three  times  the 
length  of  the  piston  stroke,  or  what  is  the  same  thing, 
six  times  the  length  of  the  crank)  f  inch.  We  mark, 
therefore,  on  line  1  a  dot  |  inch  distant  from  line  A  A. 


the  cut-off  valves  were  taken  off,  the  main  valve  would 
licgin  to  close  the  steam  port  at  9£  inches  of  piston 
stroke  and  the  cut-off  would  occur  at  17J  inches  of 
piston  stroke.  The  events  for  the  i-eturn  stroke  are 
plotted  out  in  the  same  manner  in  Fig.  154,  and  it  is 
seen  that  the  cut-off  valve  began  to  act  when  the  piston 
hail  moved  4TV  inches,  and  before  the  main  valve  had 


Fiij.   151. 


The  piston  may  then  be  moved  another  inch,  the  width 
of  port  opening  measured  and  marked  by  a  dot  on  line 
2.  The  piston  is  then  moved  to  its  third  inch,  the  port 
opening  is  measured,  and  its  width  marked  on  line  3. 

Having  continued  this  process,  we  may  draw  through 
the  dots  a  line  which  will  clearly  show  the  manner  in 
which  the  steam  port  was  opened  and  closed  ;  this 


fig.   152. 

being  shown  in  tbe  figure  by  a  full  line.  Thus  we  find, 
from  the  figure,  that  the  port  was  opened  full  when  the 
piston  had  moved  3|  inches,  and  that  the  point  of  cut- 
off is  at  the  9th  inch  of  piston  stroke.  The  manner  in 
which  the  main  valve  would  have  cut  off  steam  is 
shown  on  the  diagram  by  dots.  Thus  we  find  that  if 


fully  opened  the  steam-port,  which  is,  therefore,  never 
fully  opened.     The  action  of  the  main  valve,  after  the 


Br 

-423  4  f  65  89  to.  12    /&-/£//* 

^B 

/ 

'\ 

' 

i 

o 

/ 

\ 

i 

< 

w 

M 

/ 

Sj 

s, 

\ 

i 

| 

fj 

\ 

^ 

\ 

i 

0) 

w. 

^ 

\ 

,4 

* 

\ 

A 

-FYgr.    153. 

cut-off  valve   has  begun  to   act,   is   here   shown  by  a 

broken  line.     As  the  compression,  lead  and  exhaust  are 

^ 

\ 

^3 

6 
H 

,' 

' 

/ 

\ 

1 

' 

/ 

\ 

3 

O 

t 

/ 

7 

W 

/8 


Fig.  154 


entirely  uninfluenced  by  the  cut-off  valve,  it  is  nnneces 
sarv  to  refer  to  them  in  connection  with  its  action. 


RIDING   CUT-OFF   VAL  TAX 


113 


THE    POSITION    OH'    TIIK    Ot  T-OKF    KCC  K.STltlC. 

In  an  adjustable  cut-otT  entrine.  tin1  cut-oil  eccentric 
is  usually  fixed  upon  thecnmk  shaft.  \Vln-u  the  engine 
is  required  to  run  in  either  direction,  the  cut-off  eccen- 
tric must,  in  order  to  enable  the  engine  to  run  equally 
well  in  either  direction,  he  set  directly  opposite  (..the 


/•'/-/.    1. •>:.. 

crank.  Rut  if  the  engine  is  required  to  run  in  one 
direction  only,  there  is  some  latitude  in  the  position  in 
which  the  cut-oil  eccentric  inav  i>c  set. 


width  of  the  steam  port)  and  we  may  investigate  the 
limits,  within  which  the  position  of  the  cut-off  eccen- 
tric may  l>e  varied  as  follows:  In  Fifr.  1  .">.">,  the  circle  re- 
presents the  path  of  the  crank  pin  and  also  the  path  of 
the  center  of  the  recent nc,  the  liner;  represents  the 
throw-line  of  the  cut-ofT  eccentric,  and  TO,  that  of  the 
mam  eccentric,  the  former  being  set  at  169°  ahead  of 
the  crank  and  at  59°  ahead  of  the  main  eccentric,  whose 
angular  advance  is  20°.  The  positions  of  the  parts,  at 
the  point  of  cut-off,  is  shown  in  Fig.  156,  and  it  is  seen 
that  the  cut-off  eccentric  has  passed  the  point  x,  at 
which  it  would  move  the  valve  the  quickest,  it  follows 
therefore,  that  while  the  cut-off  valve  has  been  moving 
across  the  port  K  to  effect  the  cut-off,  the  eccentric  has 
been  moving  through  that  part  of  its  path  in  which  it 
moves  the  valve  most  rapidly.  Continuing  the  motion 
of  the,  parts,  we  have,  in  Fig.  157,  their  positions  at  the 


tig:  156. 


Let  it  be  supposed  that  the  cut-off  valves  are  so  set 
that  if  placed  in  mid-position  (as  shown  in  Fig.  148),  on 
the  main  valve,  the  edges  G  and  M  would  be  distant 


time  that  the  main  valve  cuts  off,  and  it  is  seen,  on  com- 
paring Fig.  156  with  Fig  157.  that  the  main  and  cut-off 
valves  have  moved  in  the  same  direction  and  at  nearly 


Fig.  157. 


from  the  edges  H  J  (Fig.  148),  of  the  ports  in  the 
main  valve  to  an  amount  eqiml  to  the  steam  lap  of  the 
mam  valve,  (which,  in  this  case,  is  equal  to  one-half  the 


the  same  speed.  But  at  the  moment  the  parts  are  in 
the  positions  shown  in  Fig.  157,  the  main  valve  is 
moving  faster  than  the  cut.off  valve,  for  two  reasons, 


OF  THE  '      ^\ 

[UNIVERSITY) 

GAL|WlNli>^ 


114 


MODERN  STEAM  ENGINES. 


first,  because  its  eccentric  throw-line  is  nearer  to  its 
mid-position  x.  and  second,  because  the  eccentric  moves 
the  valve  faster  and  further  while  moving  a  given 
amount  towards  and  ending  at  the  line  x,  than  it  does 
while  moving  an  equal  distance  after  passing  it. 

This  is  shown  in  Fig.  158,  in  which  L  L  represents 
the  line  of  motion  of  the  valve,  TO  the  position  of  the 
center  of  the  eccentric  when  35°  on  one  side  of  x,  and 
«  its  position  at  the  same  angle  on  the  other  side  of  x. 
Setting  a  pair  of  compasses  to  represent  the  length  of 
the  eccentric-rod,  rest  one  point  at  m,  and  mark,  on 


the  line  of  centers  L  L,  the  arc  o.  Then  rest  one  point 
of  the  compasses  at  x  and  mark  the  arc  p,  and  from  o 
to  p,  measured  along  the  line  L,  is  the  distance  the 
valve  would  be  moved  while  the  eccentric  moved  from 
m  to  x.  Rast  the  compasses  at  n  and  mark  arc  q,  and 
from  p  to  q,  on  line  L,  is  the  distance  the  valve  would 
be  moved  while  the  eccentric  moved  from  x  to  n.  The 
difference  between  the  two  amounts  of  valve  motion 
being  shown  by  the  dotted  arc  r.  Now,  suppose  that 
the  main  eccentric  is  at  »i,  and  it  is  clear,  from  the 
positions  of  the  valves  in  Pig.  156,  that  the  position  of 
the  cut-off  eccentric  must  be  such  that,  from  and  after 
the  cut-off,  it  will  move  its  valve  at  least  as  fast  as  the 
main  valve  is  moved,  or  else  the  steam-port  K  will  be 
reopened,  and  live  steam  again  admitted  until  such  time 
as  the  lap  of  the  main  valve  itself  effects  the  cut-off. 

In  Figs.  159  and  1GO,  we  have  diagrams  showing  the 
steam  distribution,  effected  with  the  eccentrics  set  as  in 
Figs.  156  and  157,  and  if  we  compare  these  diagrams 
with  those  shown  in  Figs.  153  and  154  (for  which  the 
cut-off  eccentric  was  set  directly  opposite  to  the  crank), 
we  find,  in  the  case  of  the  forward  strokes,  the  cut-off 
is  at  9  inches  in  one  case,  and  at  l.'S  inches  in  the  other; 


for  the  return  strokes,  it  is  at  9  inches  in  one  case  and 
at  16  inches  in  the  other.  We  also  find  that  from  the 
time  the  cut-off  valve  commenced  to  close  the  port, 
until  final  closure  and  cut-off  took  place,  there  was,  for 
the  two  forward  strokes,  5^  inches  of  piston  stroke  in 
one  case  and  9  inches  in  the  other,  and  it  appears  that 
by  setting  the  cut-off  eccentric  back  11°,  we  have 
delayed  the  point  of  cut-off,  and  wire  drawn  the  steam. 
The  term  wire  drawn  meaning  that  the  pressure  of  the 


\ 


\ 


\ 


\ 


s 


t'6 


Fig.    159. 


live  steam  has,  in  passing  through  the  steam  ports 
into  the  cylinder  bore,  been  reduced  by  reason  of  the 
amount  of  port  opening  being  diminished  on  account 
of  the  slow  movement  of  the  valve. 

The  reason  that  the  point  of  cut-off  occurs  at  such 
unequal  points  in  the  two  strokes,  is  that  in  this  case, 
the  cut  off  eccentric  has  been  set  in  such  position,  and 
its  rod  made  of  such  length,  as  would  give  the  longest 
point  of  cut-off  in  each  case  without  letting  the  port 
reopen. 


s 


\ 


JO 


Fig.   1  60. 


To  equalize  the  points  of  cut-off,  we  shall  require  to 
move  the  cut-off  eccentric,  and  shorten  its  rod.  In 
Fig.  161,  for  example,  the  positions  of  the  crank,  cut- 
off eccentric,  and  valves  are  shown  at  the  time  the  piston 
is  on  the  back  stroke,  and  at  its  13th  inch  of  motion 
(this  being  the  point  of  cut-off  for  the  other  stroke), 
and  it  is  seen  that  the  steam  port  L,  is  not  yet  closed. 


I!1I>1\<;  CUT-OFF  VALVES. 


II.; 


If,  to  close  it.  we  move  th>  ahead  (in- 

creasing ils  angle  will,  the  point 

of  cut-oil  for  ihc  •  if   we  lengthen  tin' 

eccentric- rod  enough  inclose-  I..  we  shall  delay  liic  point 
of  cut-oS  for  the  other   stroke  (and    that  would,    in 
case,  cause  the  port  in  reopen).     The  course  to  pursue 


a.-  in  Kig.  !.">»;  (i'oih  valves  moving  together  after  the 
point  of  cut-oil),  the  enroll'  \al\c  will  not  act  on  the 

forward  stroke  ai'ier  the  Kith  inch  of  piston  stroke,  and 
since  the  main  valve  cuts  oil  (it  the  18th  inch  of  piston 
motion  (as  is  shown  in  Fig.  1.".;;),  therefore  no  cutoff 
ran  IK-  effected  between  these  two  points. 


is  to  both  lengthen  the  rod  and  move  the  cut-oil  eccen- 


Fig.    161. 
trie  as  well,  adjusting  the  two  until  the  ports  just  escape 


Fig.  1  «;•_'.  Fig.  163. 

That  this  cannot  be  remedied  by  moving  the  cut-off 
eccentric  position,  may  lie  shown  as  follows:  Refer. 
ring  again  to  Fig.  156,  if  the  cut-off  eccentric  was 
moved  further  ahead,  its  angle  of  169  degrees  being 
increased,  the  cut-off  would  have  occured  earlier,  while 
if  this  angle  was  diminished  the  cut-off  would  not  bo 
effected  by  the  cut-off  valve,  because  it  would  not  fully 
cover  the  port. 

In  Fig.  1 62,  for  example,  it  is  moved  nearer  to  x,  and 
as  a  result  the  cut-off  is  effected  by  the  main  valve, 
Finally,  if  we  moved  the  cut-off  eccentric  to  position  x. 
Fig.  1 63,  at  the  time  the  main  eccentric  stood  at  m,  the 
cut-off  valve  would  not  effect  the  cut-off  at  all,  since 


reopening  and  the  points  of  cut-off  are  equal. 

way,  the  longest  possible  equali/ed  points  of  cut-off  are 

obtained. 

It  may  now  be  pointed  out  that  with  the  eccentrics  set 


Fi>j.  164. 

In  this  it  would  not  pass  entirely  over  the  main  valve  port. 
The  cut-off  eccentric  is  thus  shown  to  be  in  position 
to  cut-off  at  the  latest  possible  point,  without  reopening 
the  port  when  it  is  set  as  in  Fig.  156. 


116 


MODERN  STEAM  ENGINES. 


Having  limited  the  position  of  cut-off  eccentric  in 
one  direction,  we  may  now  proceed  to  find  its  limit  in 
the  other,  or,  in  other  words,  find  in  what  position  to 

'< 


and  the  crank  being  on  its  dead  center  B,  and  the  main 
valve  having  no  lead,  the  port  a  is  closed. 

In  Fig.  1 65,  the  parts  are  shown  in  the  position  they 

£=• 


A — 


Fig.    165. 


•set  it,  in  order  to  cut-off  as  early  as  possible  in  the 
piston  stroke.  In  our  previous  examples,  we  have  set 
the  cut-off  eccentric  either  at  180°,  or  opposite  to  the 


would  occupy  at  the  point  of  cut-off,  the  crank  having 
moved  but  22°.  On  continuing  the  motion,  the  parts 
will  arrive  at  the  positions  shown  in  Fig.  166,  from 


crank,  or  else  at  some  lesser  angle  ahead  of  the  crank, 
but  we  may  set  it  at  some  angle  behind  the  crank 
instead  of  ahead  of  it  (it  being  understood  that  ahead 


166. 


which  it  will  be  seen  that  the  cut-off  eccentric  being  at 
n  and  the  main  eccentric  at  m,  the-  latter  (being  nearer 
to  its  mid-position  than  n  is  to  its  mid-position)  wilj 


z 

w 

means  less  than  180°  measured  in  the  direction  of 
crank-revolution,  and  behind  the  crank  means  less 
than  180°  measured  in  the  opposite  direction  to  that 
of  the  crank  motion).  In  Fig.  164,  for  example, 
it  is  set  at  90°  behind  the  crank,  the  valve  laps,  travel, 
etc.,  remaining  the  same  as  in  the  previous  examples, 


167 


move  the  main  valve  farther  than  the  cut-off  valve  will 
be  moved,  and  it  is  clear  that  if  the  cut-off  eccentric 
were  set  at  an  angle  of  less  than  90°  behind  the  cranky 
the  cut-off  valve  would  first  effect  the  cut-off  as  in  Fig. 
166,  and  then  lag  behind  and  permit  K  to  reopen.  In 
Fig.  167,  for  example,  we  have  moved  the  cut-off 


M.;  c u T-  UJ-'F   VAL  r/.x 


117 


ecrentric  so  thut  it  stands  at  8C°  behind  tin-  crank,  ami, 
as  u   result,    i  ''  Milve,   al'ier  luiving  cut-off  the 

-ing  tin'  port  i  •  and   live 

strain  to  re enter,  as  denoted    by   tin-  arrow.      The  least 
j.c.n:  .ingle    behind     tin-    crank     for    the    cut-oil 

eccentric  ia,  therefore,  '.'0  . 

The  steam-port    opening  of  the  valves,  in    Figs.    1(M 
ami  165,  is  given  in  t  igs.  10S  and  1(3!),  where  it  is  seen 


r>'n.  168. 

that  the  ports  open  less  than  a  quarter  inch  and  close 
when  the  piston  h;is  moved  one  hall'  inch  on  the  for- 
ward and  three-quarters  inch  on  the  return  stroke. 


18 
54 

1 


/•Vr/.     109. 

W<>  have  thus  found  the  limits  within  which  the  cut- 
off eccentric  can  he  moved  on  the  shaft  in  either  direc- 
tion when  the  valves  have  the  proportions  given.  In 
the  following  examples  the  proportions  lire  as  follows  : 

Stroke  of  Piston     -  18      inches. 

Length  of  Connecting-rod 

Width  ol'   Steam  I'ort     - 
Steam  Lap 

Lead  of  Valve       -         - 
Travel  of  Main  Valve 
Travel  of  Cut-off  Valve 

In  Figs.  170,  171,  172  and  173,  we  have  the  port 
opening  when  the  eccentric  is  set  to  cut-off  at  £,  £,  A 
and  §  of  the  stroke,  the  proportions  of  the  valves  and 
ports  remaining  unchanged,  the  eccentric  having  been 
moved  upon  the  crank  shaft  in  order  to  effect  the  cut- 
off at  the  respective  points. 


i 


Here  we  find  that  when  the  cut-off  is  to  occur  at  less 
than  half-stroke,  the  rut-off  eccentric  is  at  nn  tingle  of 
less  than  lSlf/,,/i/W  the  crank,  while,  when  it  is  to  occur 
later  than  ;n  half-stroke,  the  cut-off  eccentric  is  at  an 
anglr  than  i  NO' <///<•<;./ of  the  crank,  the  extremes 

of  its  position  being  for  the  shortest  cut-off  (-J)  1 
behind  ihe  crank,  and  for  the  longest  100°  ahead  of  the 
crank,  lint  its  position,  at  the  time  the  cut-off  occurs, 
varies  but  <>°;  thus  at  the  J  rut-off,  it  stands,  at  the 
point  of  rut-off,  5°  ahead  of  its  mid-position  u;  while 
for  the  longest,  it  stands  11°  ahead,  a  difference  of  0° 
only  for  tin;  whole  range  of  cut-offs. 

But  if  we  alter  the  amount  of  lap  on  the  cul-olT 
valve,  ami  adjust  the  length  of  the  cut-off  errenlric-rod 
so  as  to  equalize  the  points  of  cut-off  for  the  two 
strokes,  we  shall  alter  the  ]  osition  of  the  cut-off  eccen- 
tric. Suppose,  for  exam] ile,  that  we  reduce  the  cut-off 
lap  to  ^  inch,  that  is  to  say,  let  the  edges  of  the  cut-off 
valve  each  come  (when  it  is  in  mid-position  as  in  Fig. 
148,)  within  ^  inch  (instead  of  the  J  inch,  in  our  pre- 
vious examples)  of  the  nearest  edges  of  the  ports,  in 
the  main  valves,  and  the  effect  is  shown  in  the  following 
figures:  In  Fig.  174,  the  cut-off  is  at  £  stroke,  and 
we  find  that  the  cut-off  eccentric  stands  5°  behind  the 
line  r,  instead  of  5°  ahead  of  it,  as  it  was  in  Fig.  170; 
also  we  find  that  the  point  at  which  the  port  begins  to 
close,  is  at  1  |  inches,  instead  of  at  1^  inches  as  before, 
thus  giving  a  greater  and  therefore  better  port  opening. 

On  the  return  stroke,  we  find  the  widest  port  opening 
in  both  cases  at  1  f  inches  of  piston  motion,  but  in  Fig. 
174.  the  port  is  a  trifle  wider  open  at  the  second  inch, 
which  is  a  slight  gain,  as  the  steam  is  less  wire  drawn. 

In  Fig.  175,  the  cut-off  being  at  $  stroke,  the  port 
openings  are  about  equal  to  those  in  Fig.  171,  and  the 
cut-off  eccentric  stands  (at  the  point  of  cut-off)  11° 
behind  the  line  v,  instead  of  1  °  ahead  of  it,  as  it  did  in 
Fig.  176.  In  Fig.  170,  (the  point  of  cut-off  being  at  £ 
stroke)  the  port  openings  are  about  the  fame  as  those 
in  Fig.  172,  the  cut-off  eccentric,  in  this  case,  standing 
at  the  point  of  cut-off  at  8°  behind  r.  instead  of  being 
ahead  of  it,  as  in  Fig.  172.  In  Fig.  177,  the  cutoff 
being  at  f  stroke,  the  cut-off  eccentric  stands  at  the 
point  of  cut-off  on  the  line  s,  instead  of  11°  ahead  of 
it,  as  in  Fig.  173.  Thus  we  find,  that  the  added  lap 
has  made  but  a  very  slight  difference  in  the  port  open- 


118 


MODERN  STEAM  ENGINES. 


Fig.  171. 


/\ 


321 


/ 

' 

\ 

\ 

/ 

^ 

\ 

\ 

\ 

/ 

\ 

/ 

/-r^ 

~-s\ 

/ 

\ 

f 
' 

/     f"f'\^ 

X\ 

/ 

\ 

• 

I  &   \ 

1  1 

^_    ]178 

i 

, 

\ 

/ 

/ 

\ 

/ 

Til 

\ 

/ 

\ 

v     / 

UyS 

\ 

/ 

/ 

X..       fl\ 

x^ 

/ 

~^' 

' 

> 

>  < 

p 

i 

t 

i  ' 

i 

\ 


12       10         8 


\ 


654321 


\ 


\ 


\ 


123456789  12        14         16        1 


Figs.   172    &    173. 


i{iin.\'i  CUT-OFF  r,i/,  r/-:x 


,UK 


119 


ings,  although  it  has  thrown    tho  rut-off  eccentric  Nick  i  les-er  cut-oil  lap.  12  inches  was  the  latest  point  at  winch 

\          \ 


1    (*      H        „ 

\ 

\       G 

ti5 

i    , 

, 

1 

r 

^VjL>V 

\ 

1 

\ 

*• 

423                                 321 

, 

Fig.    174. 

//^r\> 

, 

A 

t\ 

/v?P   \     * 

'v^ 

w 

1 

/ 

s 

\ 

/ 

' 

\ 

\  X-^_LL>/  x 
-x      |Tv«r 

\ 

/ 

~#   X 

1  3  36  JO                 65^32-1 

i> 

Fig.    175. 

in  each  case.     But  by  this  means,  the  valve  is  enabled 

the  cut-off  could  be  effected  without  reopening  the  port. 

to  cut-off  at  a  later  period  in  tiie  stroke,  without  reopen- 

It  will  be  noticed  that  both  in  Figs.  1  77  and  178,  the 

/ 

\ 

\\ 

/ 

/ 

\ 

/ 

\ 

\ 

j/yo 

[ 

\ 

\ 

/ 

/ 

\ 

, 

\ 

/ 

, 

\ 

/ 

, 

# «..'    / 


Fig.   176. 


, 

{ 

S 

/• 

\ 

f 

/ 

\ 

1 

s 

\ 
/ 

\ 

> 

( 

' 

\ 

\ 

/•234f6fi 

r  a  /0///Z 

Fig.  177. 
ing  the  ports  as  may  be  seen  from  Pig.   178,  in  which    line  is  rounded  somewhat  at  the  point  where  the  port 


the  cut-off  occurs  at   the  15th  inch,  whereas,  with  the 


begins  to  close,  and  this  occurs  because  the  main  valve 


120 


MODERN  .S'77-.MJ/   l-'.X  GINKS. 


begins  to  close  the  port  before  the  cut-off  valve  comes 
into  action,  as  may  l>e  seen  from  Fig.  179.  The 
rounded  corner  e,  Fig.  178,  shows  the  cut-oil  by  the 


or  directly  opposite  to,  the  crank,  so  that  its  position, 
with  relation  to  the  crank,  will  be  the  same,  let  the 
direction  of  revolution  be  what  it  may. 


X 


42  3  4J 


7 

e 

\ 

5> 

s 

/ 

\ 

/ 

\ 

1 

\j 

/ 

\ 

1 

/ 

X 

\ 

X 

X 

- 

- 

v. 

\ 

P  <f  '<> 


Fig.   178. 


main  valve.     The  rounded  corner/,  Fig.  178,  is  caused 
by  the  valves  acting  in  opposition  to  one  another,  the 


Fig.  179. 


main  valve  moving  in  the  direction   to  open,  and  the 
cut-off  jn  the  direction  to  close,  the  port.     It  may   now 


VARYING     THE     POINTS     OF     CUT-OFF     BY     MOVING    THE 
CUT-OFF    VALVES. 

"We  may  now  assume  the  cut-off  eccentric  to  be  fixed 
upon  the  crank-shaft,  variations  in  the  points  of  cut-off 
being  effected  by  moving  the  valves  by  means  of  a 
right  and  left  hand  screw,  which  was  shown  in  Fig.  148. 
Let  the  engine  be  required  to  run  in  oi.e  direction  only, 
and  the  proportions  to  be  as. before: 

Let  it  be  required  that  the  cut-off  be  made  adjustable' 
at  all  points  between  ^  and  -|  stroke,  and  the  first  ques- 
tion that  arises  is,  at  what  point  in  the  stroke  are  the 
two  points  of  cut-off  to  bo  equalized,  because  the  cut- 
off eccentric  must  be  set  in  such  a  position  as  to  accom- 
plish that  end  at  some  particular  point  in  the  stroke, 


X 

\ 

\^ 

/ 

\ 

/ 

N 

\ 

)^f 

1 

\ 

\ 

/ 

/ 

\ 

'      . 

\ 

/ 

/ 

\ 

X 

/ 

x 

'• 

8 


Fig.    180. 


be  pointed  out  that  if  the  engine  is  required  to  run 
backwards  as  well  as  forwards,  as  in  the  case  of  marine 
engines,  the  cut-off  eccentric  is  usually  set  at  90°  from, 


letting  the    variations  come  as  they  may  at  other  points 
of  cut-off. 

If  we  were  to  select  the  point  of  equalization  of  cut- 


l:il>I.\<;    CUT-OFF    7ALV£& 


121 


off  to  be  liiid-\v:iy  between  the  two  extren  ndf, 

or  in   cihcr  words  at  lialf  stroke,    tin-   p<  the 

parts  and  the  jiort  openings,  will  !><•  /is  in  Fig.  l.su,  hut 
when  \\e  come  to  move  the  valves  apart  \\ith  the  screw 
S.  Fig.  1  IS.  to  elTect  the  cut-oil'  a;  we  liir.l 

the   port  will   reopen  on   tin  >vhen    the   piston  is 

moving  from  the  crank  end  to  the  head  end.  am!  cut-oil 
too  early  on  the  stroke  when  the  pi>tmi  is  moving  from 
the  head  end  to  the  crank  eml. 


a  diameter  equal  to  the- travel  of  the  main  vaive,  and 
whose  <li:;  a  the  line  1!  (  '  1 1.  also  ivpr. 

piston  stn>kc>  on  some  scale;  as  the  diameter  of  the 
circle  is,  in  this  case,  3  inches  and  the  piston  stroke  is 
IS  inches,  the  scale  is  one-sixth  full  si/.e.  From  center 
('draw  a  circle  </,  whose  radius  C  (I  e<|ii.  .am 

hip  "(  'he  main  valve.  Then  mark  the  points,  distant 
from  i/  to  the  amount  of  lead  the  main  valve  is  to  have 
(in  this  case  T^  inch),  and  with  half  the  distance  C  B 


Fig.    181. 


It  is  evident,  therefore,  that  the  position  of  the  cut-off 
eccentric  must  be  adjusted  to  conform  to  the  require- 
ments of  the  longest  point  of  cut-off  required,  which  in 
this  case,  has  been  selected  at  three-quarters  of  the 
piston  stroke,  or  at  13^  inches.  Furthermore,  since  it 
has  been  shown  that  the  port  nearest  to  the  crank  is 
the  one  in  which  the  port  reopening  occurs  first,  this 
is  the  one  to  lie  dealt  with  in  finding  a  cut-off  eccentric 
position  that  will  not  effect  a  reopening  of  the  port, 
which  may  be  done  as  follows  : 

From  a  center  C.  Fig.  181,  draw  a  circle  B  D,  having 


as  a  radius,  mark  from  s  and  from  C  the  dotted  arcs 
intersecting  at  c,  draw  the  line  V,  passing  from  C, 
through  the  intersection  e,  and  this  line  will  represent 
the  throw-line  of  the  eccentric,  set  as  much  behind  the 
line  I  as  it  will  stand  ahead  of  it  when  the  crank  pin 
is  at  B,  the  path  of  crank-revolution  being  as  denoted 
by  the  arrow. 

Having  found  the  angular  advance  of  the  eccentric, 
which  is  the  angle  VIC  (equal  to  28°  in  this  case),  we 
may  proceed  to  find  the  position  of  the  crank  at  the 
time  the  main  valve  would  cut  off  steam,  and  from  this 


122 


MODERN  STEAM  ENGINES. 


we  can  then  find  the  position  .of  the  main  eccentric  at 
the  point  it  would  cut  off.  From  these  two,  we  may 
next  find  the  position  of  the  cut-off  eccentric  required 
to  cut  off  at  three-quarter  stroke,  without  reopening  the 
port. 

To  find  the  position  of  the  crank  at  the  time  the 
main  valve  would  cut-off,  we  simply  draw,  from  the 
center  C.  a  line,  passing  through  c  where  the  steam  lap 
circle  crosses  the  valve  circle  Z,  and  this  gives  us  at  H 
the  required  crank  position,  being  as  marked  132°  from 
B.  From  H  we  may  find  the  position  of  the  main 
valve,  at  the  time  it  cuts  off,  as  follows  : 

We  have  found  that  with  the  crank  at  B,  the  main 
eccentric  would  stand  28°  ahead  of  line  I,  and  as  I  is 
90°  from  B,  we  have  90°  plus  28°,  or  118°  as  the  num. 
her  of  degrees  the  main  eccentric  stands  ahead  of  the 
crank,  hence  we  mark  the  line  M'  at  118°  ahead  of  H, 
showing  the  position  of  the  main  eccentric  when  the 
crank  is  at  li  and  the  main  valve  cuts  off.  We  now 
find  the  positions  of  the  crank  and  main  eccentric  when 
the  piston  is  at  three-quarters  stroke,  because  from  these 
we  may  locate  the  necessary  position  of  the  cut  off 
eccentric.  First,  then,  we  mark  point  R  three-quarters 
of  the  distance  from  B  to  D  (this  distance  representing 
the  piston  stroke),  and  then  with  compasses  set  to  rep- 
resent the  length  of  the  connecting-rod  on  the  same 
scale  as  B  D  represents  the  piston  stroke  (one-sixth  ful] 
size),  we  mark,  from  R,  the  arc  P,  giving  at  T  the  posi- 
tion of  the  crank  when  the  piston  is  at  R.  Now  as  the 
main  eccentric  is  118°  ahead  of  the  crank  at  T,  we  may 
mark  M,  which  is  the  position  of  the  main  eccentric 
when  the  cut-off  valve  is  to  cut  off,  the  crank  being 
at  T,  and  the  piston  at  R. 

Now  while  the  main  eccentric  is  moving  from  M  to 
M',  the  cut-off  eccentric  must  move  its  valve  as  fast  as 
the  main  eccentric  moves  its  valve,  and  all  we  have  to 
do  is  to  find  where  to  place  it  in  order  to  enable  it  to 
do  so,  which  we  may  accomplish  as  follows  : 

If  we  draw  from  x,  as  a  center,  a  semi-circle  G,  having 
a  radius  x  M',  we  shall  find  at  a  the  position  of  the 
cut-off  eccentric  at  the  time  the  main  valve  has  arrived 
at  M'  and  would  cut-off  the  steam,  and  from  this  point 
a  we  may  obtain  the  position  of  the  cut-off  eccentric  at 
the  time  its  valve  is  to  cut-off  by  setting  the  compasses 
to  the  distance  between  M  and  M',  measured  on  the 


circle,  and  marking  from  a  an  arc  n,  from  which  we 
may  mark  line  N,  giving  the  position  for  the  cut-off 
eccentric  at  the  point  of  its  valve's  cut-off,  the  crank 
lieing  at  T,  the  piston  at  R  and  the  main  eccentric  at 
M.  Now  suppose  the  piston,  the  crank  and  the  main 
and  cut-off  valves  to  stand  in  these  respective  positions, 
and  the  cut-off,  by  cut-off  valve,  will  occur  while  the 
main  eccentric  is  at  M  and  the  cut-off  eccentric  is  at  X. 
and  being  nearer  to  its  mid-position  x  than  M  is  to  its 
mid-position  x,  therefore  N  will  move  its  valve  fastest 
and  the  port  cannot  reopen. 

While  the  main  eccentric  moves  from  M  to  M',  the 
cut-off  eccentric  moves  from  N  to  a,  being,  at  each 
point  in  its  movement,  nearer  to  .r  than  M  is,  and  there- 
fore moving  its  valve  faster.  On  arriving  at  a,  how- 
ever, N  and  M  will  be  equi-distant  from  x,  and  they 
will  move  their  valves  at  equal  speeds.  At  this  time, 
however,  the  main  valve  will  have  closed  the  port  and 
reopening  cannot  occur. 

Having  found  the  positions  for  the  crank,  the  main 
eccentric,  and  the  cut-off  eccentric,  at  the  time  of 
cut-off  on  the  piston  stroke  from  B  to  D,  the  crank 
having  started  from  B,  and  moved  to  T,  we 
may  now  find  the  corresponding  positions  for  the 
valves.  In  the  upper  half  of  Fig.  182.  \v<>  have  marked 
the  positions  of  the  crank,  the  cut-off  eccentric  and 
the  main  eccentric,  simply  transferring  them  from  Fig. 
181.  To  find  the  corresponding  positions  of  the  main 
valve,  we  mark  from  the  main  eccentric  position,  the 
dotted  line  m  p,  giving  the  point  p.  Now  since  the 
line  B  D  represents  the  stroke  of  the  valve,  and  line  x, 
the  valve's  mid-position,  therefore  the  radius  from  p  to 
the  line  x,  measured  on  the  line  B  D,  is  the  distance  the 
main  valve  must  have  moved  from  its  mid-position, 
when  the  main  eccentric  stands  at  m. 

Now,  if  the  center  of  the  main  valve  stood  on  the 
line  X,  it  would  be  in  mid-position,  and  all  we  have  to 
do  is  to  mark  from  X,  a  line  P  distant  from  X  to  the 
same  amount  that  p  is  distant  from  the  line  x  x  and 
from  this  new  center  P,  we  draw  in  the  main  valve. 

The  cut-off  valve  we  draw  in  position,  to  just  close 
the  port  K  at  the  crank  end.  For  the  return  stroke,  we 
draw,  on  the  lower  half  of  the  cut,  B  D,  representing  the 
valve  travel,  and  also  the  piston  stroke  as  before:  then 
mark  the  piston  position  R,  at  the  point  of  cut-off,  and 


1:11>1S<.; 


VAL 


123 


from    this  obtain   tin-    OVUM  -    in    previous 

uxiimpies.     J-'roni  don,  we  mark  the  main 

ttl  rir    throw-line    m,    11J  -    the. 

•  :T    eceentnr    throw -line    HIJ    ahead    of  the    main 

From  nt,  we  ilr;i\v   the   line  r,  showing  what 

-lain  valve    has    moved     from  its   mid-posi- 

-   distance     !.e!Ilur     1'roIM   /'    to  X,     measured   ,   Q 

line  I!  1>.  or  in  other  words,  from  /•  to  lice  ecu; 

circle.       \\'e  trail.- I'er   this  distance    from    X,  oi.tainnii:   I' 


cut-ofi  valves,  and  from  this  we  can  easily  ascertain  the 
lap. 

Now  in  moving  from  the  point  of  cut-off  on  one 
stroke  to  that  of  the  other,  the  cut-off  eccentric  has 
moved  from  >i  in  the  upper  half  to  n  in  the  lower  half 
of  the  figure,  the  difference  in  its  distance  from  mid- 
posit  tig  shown  by  the  dotted  lines  E  F;  all  we 

have  to  tin  then,  is   to  draw   a   (lotted   line  C   from  the 
«!   the  valve  iii  the  upper  half  of  the  figure,  and 


as  .a  center  wherefrom  to  draw  in  the  main  valve,  and 
we  thondraw  in  tho  cut-off  valve  "W",  in  position  to  just 
close  the  port;  knowing  that  to  be  its  position  at  the 
point  of  cut-off,  and  corresponding  to  the  positions  of 
the  crank  and  the  eccentrics. 

II nving  found,  for  both  piston  strokes,  the  positions 
of  the  main  and  cut-off  valves  at  the  point  of  cut-off 
we  may  find,  therefore,  the  amount  of  lap  the  cut-off 
valves  are  given  by  this  constuction,  the  method  being 
as  follows:  "We  have  in  the  lower  half  of  Fig.  182, 
the  valves  in  position  at  the  point  of  cut-off  for  the 
return  stroke,  or  while  the  piston  is  moving  from  the 
head  end  of  the  cylinder  towards  the  crank,  and  we 
require  to  find  the  position  of  the  cut-off  valve  Z,  on 
the  lower -half  of  the  diagram,  because  this  will  give 

us  the  distance  between  the  two  outside  edges  of  the 
IS 


draw  in  the  cut-off  valve,  letting  its  edge  M  be  put 
back  from  dotted  line  C,  to  an  amount  equal  to  the 
distance  between  the  lines  E  F,  and  the  positions  of  the 
eccentrics  and  both  valves  will  be  shown  on  the  lower 
half  of  the  figure. 

To  find  the  amount  of  cut-off  lap,  subtract  the  width 
apart  M  G,  of  the  cut-off  valves  from  the  width  apart  of 
the  inside  edges  of  the  main  valve  ports,  or  in  other 
words,  from  distance  y  in  Fig.  182. 

If  we  move  the  cut-off  valves  apart,  by  means  of  the 
adjusting  screw,  sufficient  to  effect  the  cut-off  at  half 
stroke  on  the  forward  stroke,  the  point  of  cut-off  will  be 
at  1 0  inches  on  the  return  stroke,  as  is  seen  on  the  dia- 
gram of  the  port  openings  in  Fig.  183. 

By  moving  the  valves  still  further  apart  to  effect  the 
cut-off  at  ^  stroke,  there  is  a  variation  of  |  inch  in  the 


124 


MODERN  STEAM  ENGINES. 


two  points  of  cut-off,  as  is  seen  in  the  diagrams  of  the 
port  openings  in  Fig.  184.  This  may  be  obviated,  to 
pome  extent,  by  giving  to  the  screw-thread,  that  moves 
the  cut-off  valve  "W,  a  coarser  pitch  than  the  thread 
that  moves  Z,  so  as  to  move  it  more,  a  plan  that  is  not 
infrequently  resorted  to. 


main  valve  and  the  crank,  at  the  point  of  cut-off,  by 
the  construction  in  Fig.  185,  which  is,  in  this  respect, 
merely  a  repetition  of  former  examples;  B  D  represents 
the  full  travel  of  the  main  valve,  and  the  large  circle 
the  path  of  the  crank  drawn  to  scale;  d  is  the  lap 
circle.  <l  a  is  the  valve  lead,  VIC  the  angular  advance 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


/•'/</.   183. 


It  will  be  noted  that,  throughout  the  whole  of  the 
diagrams  of  the  cut-off  valves,  the  steam  port  openings 
are  grealy  reduced  by  the  action  of  the  cut-off  valve, 
which,  assuming  the  full  area  of  the  steam  port  to  be 
required  for  the  admission,  causes  the  steam  to  be  wire- 
drawn, especially  at  the  early  points  of  cut-off.  This 
may,  to  some  extent,  be  remedied,  by  giving  to  the 
cut-off  valve,  an  increase  of  travel. 


of  the  main  eccentric  (placed  for  reasons  already  ex- 
plained, behind  instead  of  ahead  of  the  line  I).  H  is  the 
position  of  the  crank,  and  m'  the  main  eccentric,  these 
two  latter  standing  in  the  position  they  would  occupy 
at  the  time  the  main  valve  would  effect  the  cut-off;  i\  is 
the  position  of  the  piston  at  the  time  we  wish  the 
cut-off  valve  to  effect  the  cut-off,  and  T  the  crank 
position  corresponding  to  piston  position  R.  We  mark 


A 


\ 


\ 


/ 


A 


Fig.    1  84. 


It  has  been  shown  that,  in  a  simple  slide-valve,  the 
port  openings  may  be  increased  by  increasing  the 
amount  of  valve  travel,  but  when  a  cut-off  valve  is 
used,  it  is  not  permissible  to  give  the  main  valve  over- 
travel,  because  the  main  valve  would  then  begin  to  close 
the  port,  instead  of  permitting  the  cut-off  to  be  effected 
entirely  by  the  cut-off  valve.  The  effect  of  giving  to 
the  cut-off  valve  more  travel  than  the  main  valve,  and 
the  method  of  finding  the  positions  of  the  eccentrjcs 
for  any  given  amount  of  cut-off  valve  overtravel,  iis 
shown  as  follows:  We  first  find  the  positions  of  the 


m  behind  m'  to  the  same  amount  that  T  is  behind  H, 
and  thus  have  the  positions  of  the  crank  and  of  the 
main  eccentric,  at  the  time  the  cut-off  valve  is  to  effect 
the  cut-off.  To  find  the  position  for  the  cut-off  eccentric, 
we  mark  arc  Q  Q,  distant  from  the  circle  B  D,  to  half 
the  amount  of  overtravel  of  the  cut-off  valve,  (hence 
as  Q  Q,  is  £  inch  from  circle  B  D,  the  cut-off  valve  will 
have,  in  this  case,  an  inch  more  travel  than  the  main 
valve). 

We  then  set  a  pair  of  compasses  to  the  radius  xm, 
on  circle  B  D,  and  transfer  it  to  circle  Q  Q,  getting  the 


RJL>J\t;    CL'T-U  !•'!•'    Y. \LVES. 


126 


radius  x  a.     Then  transfer  the  radius  m'  m  from  a.  and     linos  the  cut-off  at  one-quarter  stroke,  and  it  is  seen,  on 


get  arc  n  on  Q  Q,  from  whir  or  the  position  for 

the  cut-oil  eccentric,  at  tho  tiiuu  iu>  valve  is  to  cut-off. 


comparing  these  with  previous  examples,  that  the  port 
openings  are  improved.     At  the  three-quarter  stroke,  the 


The  method  of  finding  the  required  amount  of  lap  on  the 
cut-off  valve,  is  tlir-  same  as  has  already  been  explained 
with  reference  to  Fig.  182,  hence  we  may  now  examine 
the  port  openings  given  by  the  new  condition,  viz.,  one 


1     2     1    4     1    «    7_i 

9    10        12        14        16        f 

/ 

' 

, 

. 
t 

\ 

) 

/ 

' 

' 
> 

/ 

/ 

- 

' 

\ 

' 

/ 

• 

/ 

8        16         14         12        10  9    1 

6543 

Fig.   186. 

inch  of  overtravel  for  the  cut-off  valve.  Fig.  186 
shows  in  the  full  lines  the  port  opening  for  the  cut-off 
at  three-quarter  stroke;  Fig.  187  shows  in  the  full  lines 
the  cut-off  at  half -stroke,  and  Fig.  188  shows  in  the  full 


185. 


port  openings  are  considerably  increased,  and  reopening 
avoided.  At  half  stroke  the  port  openings  are  also 
increased,  as  may  be  seen  by  a  comparison  with  Fig. 
183,  while  at  one-quarter  the  openings  are  wider  at  the 


/ 

'. 

\ 

\ 

\ 

\ 

/ 

• 

•^ 

» 

/ 

/ 

/ 

\ 

• 

• 

• 

/ 

• 

• 

- 

Fig.   187. 

2nd  and  3rd  inch  of  piston  motion  on  the  forward 
stroke,  but  about  the  same,  on  the  back  stroke  as  those 
in  Fig.  184. 

But  we  may  further  increase  the  port  openings  by 


or  ' 

UNIVERSITY 

OF 


126 


MUDI-:U.\  STEAM  E.\U 


giving  to  the  cut-off  valve  a  further  increase  of  travel, 
making  it  5  inches  instead  of  4  inches,  and  leaving  the 
main  valve  at  its  original  stroke  of  3  inches.  The  port 
openings,  with  5  inches  of  cut-oft  valve  stroke,  are 
marked  on  the  three  last  diagrams  in  dotted  lines,  and 
it  is  seen  that  the  increase  is  considerable  in  the  longer 
points  of  cut-off,  but  not  so  great  in  the  shorter  ones. 
and.  also,  that  the  points  of  cut-oil  are  more  nearly 
equalized  for  the  two  strokes,  let  the  cut-off  occur  where 
it  may.  It  is  usual,  therefore,  to  give  to  the  cut-off 
valve  more  travel  than  the  main  valve,  and  from  what 
has  been  said,  the  student  may  readily  plot  out  diagrams 
from  any  given  dimensions,  and  work  out  the  port 
openings  for  himself. 

To  obtain  a  wider  steam  port  opening,  and  therefore 
a  fuller  supply  of  steam,  previous  to  the  point  of  cut- 
off (an  object  that  is  of  great  importance  when  the 


1     2  4K  4?i  2    1 

Fig.   188. 

cut-off  is  to  occur  at  early  points  in  the  stroke), 
double  or  treble  ported  valves  may  be  employed, 
such  valves  being  called  griddle  valves.  Thus  the  form 
of  valve  in  the  foregoing  figures  may  l>e  double  ported, 
doubling  the  port  openings,  or  the  same  amount  of  port 
opening  may  be  had  with  less  valve  travel. 

In  Fig.  189  is  shown  an  example  of  griddle,  or 
multi-ported,  valves,  the  main  valve  having  the  two 
ports,  K  and  L,  on  its  face,  and  the  four,  g  h  p  g,  on  its 
back.  The  cut-off  valve  has  four  corresponding  ports 
(v  u  t,  etc.),  and,  as  only  one  cylinder  port  can  admit 
steam  at  one  time,  a  full  supply  of  live  steam  is  ob- 
tained so  long  as  the  combined  openings  of  the  ports, 
g  h  p  q,  equal  the  port  opening  of  the  cylinder  steam 
port.  Thus,  if  the  cylinder  ports  are  an  inch  wide, 
and  the  ports,  g  h  p  q,  are  each  one-quarter  open, 
the  total  opening  will  be  an  inch,  because  the  four 
quarters  equal  an  inch,  and  if,  at  this  point  in  the  piston 


motion,  the   cylinder  port  is  open  an  inch,  the   steam 
supply  is  not  decreased  by  the  cut-off  ports. 

The  ports  in  the  cut-off  valve  are  made  wider  than 
g  h,  etc.,  in  the  back  of  the  main  valve,  because  by  this 
means  the  cut-off  eccentric  is  brought  into  a  better  posi- 
tion to  effect  a  quick  cut-off  and  avoid  wire-drawing, 
as  will  be  understood  from  Fig.  190,  in  which  the  full 
lines  represent  the  ports  in  the  cut-off  valve  made  twice 
as  wide  as  those  in  the  back  of  the  main  valve,  and  the 
dotted  lines  show  the  cut-ofi  ports  if  made  of  equal 
width  with  the  main  valve  ports  y  Jt,  etc.  The  main 
eccentric  is  at  m.  and  with  the  cut-off  ports  made  twice 
as  wide  as  g  h,  the  cut-off  eccentric  will  be  at  «,  when 
the  valves  are  in  the  positions  shown,  and  when  the 
cut-off  takes  place  the  cut-off  eccentric  will  have  arrived 
at  a'.  Thus  it  will  be  seen  that  through  widening  the 


/•'/-/.    189. 

ports  in  the  cut-off  valve,  the  cut-off  has  been  effected 
with  the  cut-off  eccentric  in  the  most  desirable  position 
for  cutting  off  quickly. 

Now  suppose  that  the  ports  in  the  cut-off  valve  were 
as  denoted  by  the  dotted  lines,  or  in  other  words,  were 
cf  equal  width  with  those  in  the  back  of  the  mam 
valve,  and,  in  that  case,  the  cut-off  eccentric  will  be  at 
re  when  the  cut-off  is  effected,  the  port  edges  «  I  <•  <l  of 
the  cut-off  valve  having  closed  ports  g  //,  etc.,  and  the 
cut-off  valv«*  will  not  have  been  moved  so  quickly, 
hence  the  steam  would  be  more  wire-drawn.  Another 
and  important  consideration  is  that  in  order  to  effect 
the  cut-off  at  late  points  in  the  stroke,  the  cut-off  eccen- 
tric would  require  to  be  placed  nearer  to  the  main 
eccentric,  and  the  two  would  travel  at  a  more  nearly 
equal  speed,  causing  a  very  slow  cut-off  port  closure, 
and  therefore,  great  wire-drawing. 

This  may   be   seen   as    follows:     Taking  the  dotted 


CLTOFF  r.i/,r/-:.v. 


127 


lines  to  r.  :  ho  cut-off  va'.v  .i-ofl 

::k  at  '!'.    fin-  main  eccentric 
centric  al 

oil  i  ace  a:  :i   later   point  in  the   crank   path,  we 

must  put  the  cut-oil  valve  back,  (or  to  the  right  of  the 


when  at  the  point  of  cut-off.     Tt  being  assumed  that 
cut-oil  valve  is  to  be  set  to  cut-off  at  its  longest  point 
at  i  imp  as  the   main  would  cut-off,  we  may 

a  corresponding  position  of  the  cut-off  eccen- 
tric   from  that  of  the  main  eccentric  as  follows:     In 


fiirirei.  an<l  to  ilo  this.  we  must  pur  the  cut-off  eccentric 
n  luck,  or  nearer  to  the  main  eccem  ric  m,  causing  Ixith 
valves  to  travel  at  a  nearly  e<|ual  speed  and.  as  before 
state' i.  i  a  very  slow  cut-off  ]iort  closure. 

Tin-  extra  width  of  the  cut-off  valve  ports  must  be 
situated  equally  on  each  side  of  the  ports  in  the  main 


Fiy.    191. 

valve  when  the  tffo  valves  are  placed  in  mid-position, 
as  in  Fig.  189,  so  that  the  ports  may  all  close  simulta- 
neously, as  in  Fig.  191. 

To  investigate  the  action  of  the  valves,  and  locate 
the  positions  of  the  eccentrics  for  any  point  of  cut-off, 
we  first  find  the  positions  of  the  various  parts,  at 
the  point  of  cut-off  by  the  construction  shown  in  pre- 
vious examples,  and  repeated  in  Fig.  192,  H  being  the 
position  of  the  crank,  and  m  that  of  the  main  eccentric 


190. 


Fit:.  193,  we  have  the  positions  of  the  valves  corres- 
ponding to  crank-pin  position  II.  and  main  valve  posi- 
tion m  in  Fig.  192,  and  in  Fig.  194,  we  have  the  ports 
t  u  v,  etc.,  in  the  cut-off  valve  twice  as  wide  as  those  in 
the  back  of  the  main  valve,  and  it  will  be  found  that 
the  cut-off  eccentric  must  beset  in  advance  of  the  main 
eccentric,  sufficently  to  move  the  cut-off  valve  the  dis- 
tance e.  or  that  between  i\w  dotted  lines  W  and  Z,  the 
former  being  fair  with  the  outside  edge  of  the  main 
valve  port,  -and  the  latter  fair  with  the  opposite  edge  of 
the  cut-off  port.  Supposing  the  ports  g  J>,  etc.,  to 
measure  ^  inch,  and  ports  t  u  v,  etc.,  to  measure  an 
inch,  and  the  distance  r  (the  two  valves  being  placed  in 
their  mid-positions)  will  measure  J  inch.  Continuing 
the  construction  of  the  diagram,  Fig.  192,  we  draw  the 
line  G,  passing  from  m  to  line  B  D,  and  at  a  right  angle 
to  it.  Then  on  line  B  D,  measure  off  from  G  the  dis- 
tance e,  Fig.  194,  and  draw  line  n',  giving,  at  its  inter- 
section with  the  outer  circle,  the  location  of  the  cut-off 
eccentric  as  shown  by  the  line  n  n. 

The  construction  is  simple  enough  when  we  consider 
that  the  line  B  D  represents  the  valve  travel  full  size, 
and  Fig.  194,  the  valves  one-quarter  full  size,  and 
that  the  main  eccentric  being  at  m  (Fig.  192),  we  have 
by  lines  G  n',  (distant  apart  equal  to  four  times  e,  or  J 
inch  in  this  example)  found  a  position  for  the  cut-off 


12S 


MODERN  STEAM  ENGINES. 


eccentric  n  n  ,  that  would  move  the  cut-off  valve  £ 
inch  as  required.  Suppose,  now,  that  it  were  required 
to  find  the  position  of  the  cut-off  eccentric,  when  the 


center  C,  the  arcs  c.  A  line  V  drawn  through  C  c, 
gives  the  angular  advance  of  the  main  eccentric. 
From  c,  on  V,  we  draw  the  circle  X,  and  from  C, 


piston  is  to  have  its  steam  cut  off  at  half-stroke,  and 
we  draw  a  circle  B  D,  Fig.  195,  equal  in  its  diameter  to 
the  stroke  of  the  valve,  and  a  circle  d  whose  radius 


193. 


equals  the  amount  of  lap  on  the  main  valve.  "We 
mark  point  S  distant  from  d  to  the  amount  of  lead  the 
main  valve  has.  "With  a  radius,  equal  to  one-half  the 
radius  of  circle  B  D,  we  mark  from  S,  and  from  the 


192. 


through  c.  where  circles  d  and  X  intersect,  we  get  at  H 
the  position  of  the  crank  at  the  time  the  main  would 
cut  off. 

To  find  the  corresponding  position  of  the  main  valve, 
we  add  to  90°  the  angle  V  I,  whatever  it  may  be  (in 
this  case  it  is  28°  as  marked)  and  get  at  ?»'  (118°  from 
H),  the  position  of  the  main  valve  at  the  time  it  would 
cut  off  the  steam,  independently  of  the  cut-off  valve. 
We  have  next  to  find  the  position  of  the  cut-off  ecron- 
tric,  when  set  to  cut  off  at  the  same  point  as  the  main 
valve,  and  to  do  this,  we  draw  from  in'  line  G.  "We 
then  take  the  full  distance  the  edge  of  the  cut-off  valve 
stands  from  the  edge  of  the  main  valve  (when  both 
valves  are  in  mid-position  as  denoted,  by  e  in  Fig.  195), 
and  mark  line  n'  distant  from  G  to  the  amount  of  e, 
Fig.  195,  and  this  gives  us  the  point  n"  on  the  outer 
circle,  and  from  this  we  draw  the  line  n"  n",  which  is 
the  position  of  the  cut-off  valve,  when  the  crank  is  at 
H,  and  the  main  valve  at  m'.  Then  we  mark,  at  T,  the 
position  of  the  crank  when  the  piston  is  at  half-stroke, 
and  it  is  clear  that,  having  moved  the  crank  back  from 


L'/l>/.\<;   CUT-OFF  VALVES. 


1 


129 


II  to  T,  wo  must  move  the  main  ami   rut-off  eccentrics  i       Now  suppose   tlio  positions  of  the  rrank   and   ercrn- 


back   an  equal   distance,    hence.    with   compasses   set    to 


radius  II  T,  wo  mark  fro:         '  which 


position  of  the   main    eccentric   when    the   piston  is  at 


en  determined  by  this  mothod,  the  cut- 
off valve  ports  l.eing  1  inch  wide,  those  iii  the  Lack  of 
the  main  valve  .1  inch  wide,  the  cylinder  ports  being  1 


half  stroke,  and  with  the  same  radius  we  mark  from  n" 
point  n,  which  is  the  position  of  the  cut-off  eccentric 
when  the  piston  is  at  half  stioke.  The  proof  of  the 
construction  is,  that  the  two  eccentrics  stand  at  30° 


w T        fr\ 

K_x  ^ . 


l-'i'j.    19-1. 

apart  in  either  case,  and  the  main  eccentric  is  118° 
ahead  of  the  crank,  hence  we  have  merely  first  found 
the  position  of  the  parts  when  the  main  valve  cuts  off 
and  then  moved  them  all  back  together  to  get  their  posi- 
tion at  another  point  of  cut-off. 


195. 


inch,  the  main  valve  having  %  inch  steam  lap  and  ^ 
lead,  the  travel  of  both  valves  being  obtained  by  add- 
ing the  width  of  the  port  to  the  amount  of  the  steam 
lap  and  then  multiplying  by  2  (this  amount  of  travel 
being  sufficient  to  let  the  main  valve  fully  open  the 
steam  ports) ;  suppose  also  the  main  and  cut-off  eccentrics 
to  be  so  set  on  the  shaft  that  with  the  cut-off  eccentrics 
moved  as  close  together  as  possible,  both  will  cut-off 
the  steam  at  the  same  point  in  the  stroke,  and  the  crank 
being  at  H,  Fig.  195,  the  main  eccentric  will  be  at  mf 
and  the  cut-off  at  n",  and  the  port  openings  will  be  as 
in  Fig.  196  (these  openings  having  been  obtained,  as  in 
previous  examples,  by  moving  an  engine  piston  and 
measuring  the  port  opening  at  each  inch  of  piston 
motion). 

It  is  seen  from  this  diagram  that  up  to  the  eleventh 
inch  of  piston  motion,  the  admission  is  as  free  as  if  no 
cut-off  valve  were  employed,  since  the  amount  of  port 
opening  is  equal  to  that  given  by  the  main  valve.  The 
admission  is,  therefore,  more  free  and  the  cut-off  more 


130 


MODERN  STEAM  ENGINES. 


sharp  than  in  the  cases  in  which  the  main  valve  had 
but  one  port..  We  have  now  to  consider  the  means  by 
which  the  valves  are  to  be  enabled  to  cut  oil  at  other 
points  in  the  stroke,  and  this  can,  in  the  case  of  a  single 
cut-off  valve,  as  in  the  examples  now  under  considera- 


> 

"* 

> 

\> 

s 

" 

^ 

s 

/ 

/ 

/ 

x 

V 

\ 

\ 

/ 

\ 

> 

s 

7) 

/2  to  $  > 

Fig.  196. 

tion,  be  done  by  increasing  the  stroke  of  the  main 
valve,  whereas  if  two  cut-off  valves  were  used  on  the 
back  of  the  main  valve,  the  earlier  points  of  cut-off 
must  be  effected  by  means  of  moving  them  apart  by  a 
screw,  such  as  in  Fig.  148. 

Now  suppose  that  the  eccentrics  having  being  set  by 
the  construction  given  in  Fig.  195  (the  longest  point  of 
cut-off  effected  by  the  cut-off  valve  equalling  the  point 
at  which  the  main  valve  cuts  off),  and  suppose  that  we 
increase  the  main  valve  travel  sufficiently  to  effect  the 


\ 


\ 


\ 


Fig.   197. 

cut-off  at  half-stroke,  and  we  shall  find  that  the  admis- 
sion will  occur  as  in  Fig.  197,  the  port  closure  from  the 
first  to  the  sixth  inch  of  piston  motion  occurring  be- 
cause the  extra  travel  given  to  the  main  valve  causes 
its  port  edge  to  partly  cover  the  port  K,  as  in  Fig.  198. 
This  may  ooviously  however,  be  remedied  by  cutting 
away  that  edge  as  in  Fig.  199,  which  will  not  affect  in 
any  other  way  the  action  of  the  valve. 

To  find  the  amount  the  travel  of  the  main  valve  must 
be  increased  to  effect  the   cut-off,  at  some  earlier  point 


in  the  piston  stroke,  as  say  for  example,  at  half-stroke, 
we  proceed  as  in  Fig.  200,  in  which  the  position  of  the 
crank,  when  the  piston  is  at  half-stroke,  and  the  corres- 
ponding positions  of  the  main  and  cut-off  eccentrics, 
are  found  by  the  same  construction  as  in  previous 


•(• 


198. 


examples.  Now,  it  will  be  found  that  if  we  place  the 
two  valves  in  their  mid-positions,  the  amount  the  throw 
(not  the  travel)  of  the  main  eccentric  must  be  increased, 
in  order  to  change  the  point  of  cut-off  from  what  it 
was  in  Fig.  196,  to  half  piston  stroke,  will  be  equal  to 
the  distance  e,  Fig.  201,  and  as  the  position  of  the  cut- 
off eccentric  will  not  be  influenced  by  increasing  the 


199. 


main  eccentric  throw,  we  draw  a  line  n',  on  the  diagram 
Fig.  200,  and  from  this,  a  second  line  G,  distant  from 
n'  the  amount  represented  by  e,  in  Fig.  201,  (which 
being  -f^  inch,  and  the  illustration  being  one-quarter 
size,  makes  the  distance  from  «'  to  G  become  £  inch) 
we  then  draw  an  arc  J  J,  passing  through  the  point 
where  line  G  and  the  cut-off  eccentric  throw-line  inter- 
sect, and  the  distance  between  the  circle  and  the  arc 


CL'Tol-T    VALVES. 


131 


J  J.  or  radius  <i,  is  the  amount  tho   throw  of  the  eccen- 
tric must  in-  increa.-ed.  in  effect    the   cut-off  ill 
piston    stroke.      I'.y   increasing    the  throw  of  the 


increased   its  lead,   making  it  j   inch  instead   of   ^  as 

re.      The    jiorl     openings,    with     the    cui  ,,tT  at  half 

stroke,  arc  shown   in   rig.  'jo:!,  and  it  is  seen  that  in- 


i'. n trie,  we  have  merely  put  the  main  valve  further 

back.  as  will  1«;  understood  from  Fig.  202,  in  which 
with  both  eccentrics  having  the  same  throw,  the  valves 
would  occupy  the  positions  they  occupy  in  the  figure; 
but  by  increasing  the  throw  from  the  circle  to  arc  J, 


tig.  201. 

(Fig.    200),  .we   have   pushed  the  main  valve  back,  so 
that  the  cut-off  will  be  effected. 

\Ve  have,  also,  by  increasing  the  main  valve  travel. 
17 


200. 


creasing  the  stroke  of  the  main  valve  has  made  the 
steam  port  open  full  at  1 1  inches  of  piston  motion  for 
one  stroke,  and  at  1  £  inches  of  piston  motion  for  the 
other,  which  is  a  great  advantage,  while  the  ports  have 
remained  wide  open  to  5^  inches  of  piston  motion  on 
one  stroke,  and  6|  inches  on  the  other.  The  points  of 


jj^J  ''  ^ J  ''  '   ,       J  '< 


Fig.  202. 

cut-off  also,  are  very  nearly  equalized,  and  it  is  clear 
that  the  steam  distribution  has  been  greatly  improved, 
as  may  be  seen  on  a  comparison  with  previous  figures. 


132 


MODERN  STEAM  ENGINES. 


To  find  the  throw  of  the  main  eccentric  necessary,  in 
order  to  cut  off  the  steam  at  one-quarter  stroke,  we 
find  the  crank  position  with  the  piston  at  quarter  stroke, 


\ 


\ 


I 


Fig.  203. 

as  in  Fig.  204,  and  then,  by  the  construction  explained 
with  reference  to  Fig.  195,  find  the  corresponding  posi- 
tions of  the  main  and  cut-off  eccentrics.  We  then 
draw  the  line  n',  and,  from  this,  mark  point  G  distant 
from  n'  the  amount  represented  by  c  in  Fig.  201, or  in 
this  case,  £  inch.  From  G  we  mark  the  arc  J,  and  the 


Least  or  normal  travel  of  main  valve,     -    -  3  in. 

Travel  of  main  valve  to  cut  off  at  half  stroke,  3£  " 

"       "  "      "    "  one-quar.  "    4|  ''• 

Increasing  the  main  valve  travel  to  4^  has,  however, 
again  increased  the  lead,  making  it  §  inch  full. 

In  I^ig.  205,  we  have  the  port  openings  for  the  cut- 


Fig.  205. 

oil  at  one-quarter  stroke,  and  it  is  seen  that  they 
are  much  greater  than  in  Fig.  184,  where  a  single- 
ported  cut-off  valve  was  used. 

If  two  separate  main,  and  two  separate  cut-off,  valves 


Fig.  204. 


radius  a  is  the  amount  of  increased  travel,  above  that 
required  for  the  longest  cut-off,  necessary  to  cut  off  at 
one-quarter  of  the  piston  stroke. 

As  the  radius  a,  measures  in  this  case  T9T  inch,  the  in- 
crease in  the  valve  travel  is    ,  and  we  have: 


are  employed,  being  connected  by  arms  A  and  B,  Fig. 
206,  the  construction  is  the  same  except  that  the  valve 
does  not  need  the  outer  ribs  X.  X'  in  Fig.  1 93,  which 
are  necessary,  in  that  case,  to  close  the  end  ports  in  that 
figure  ;  it  being  obvious  that,  in  the  absence  of  X',  the 


I:H>I\<;  CUT-OFF   \'.\L  vr.s. 


133 


Ifft  hand   port  in  the    main   valve  wmtld    )»•   left   o[>en.  I  .me  and  a   half  times  the  width  of  the  steam  port,  and 
while  the  others  are  close.  1.      In    Fig.  lint;,  however,  ilie  |  the  valveexhaiist  pm-t  (<n;  more  properly,  exhaustr./ 


Fig.  206. 

cut-off  ports -for  one  cylinder  port  beta  <-d  from  I  need  only  equal  the  width  of  the  cylinder  exhaust  port 

those  of  the  other  (!>y  reason  of  separate  valves  lx>ing  |  added  to  twice  the  width  of  the,  bridge.     It  may  also 


used),  the  cut-off  valves  need  not  bridge  the  end  ports 
g  q.      in  all  other  respects  the  valves  are  essentially 


Fig.  208. 

alike,  and  so  also  is  their  action,  which  may  be  investi- 
gated in  the  same  manner,  and  (under  equal  conditions) 
with  like  results,  by  means  of  the  diagrams  already 
explained.  It  may  be  pointed  out,  however,  that  the 
exhaust  ports,  in  the  main  valves  and  in  tho  cylinder, 
need  not  be  so  wide  where  two  main  and  two  cut-off 
valves  are  used,  because  they  act  for  one  steam  port 
only,  hence  the  cylinder  exhaust  port  need  only  equal 


207. 


be  noted  that  were  it  not  that  the  main  valve  stroke  is 
increased  in  order  to  effect  the  earlier  points  of  cut-off, 
the  cylinder  exhaust  port  would  only  require  to  be  of 

/6 


> 

^ 

\ 

/ 

x 

\ 

/ 

\ 

/ 

\ 

\ 

y 

\ 

X 

/6 

Fig.  209. 

the  same  width  as  the  cylinder  steam  ports.  The  ports 
K  L,  in  the  main  valve,  are  made  wider  than  the  cylin- 
der ports  a  and  b,  so  that  they  may  not  unduly  close 
them  when  the  main  valve  stroke  is  increased  to  effect 
the  earlier  points  of  cut-off,  a  matter  that  was  explained 
with  reference  to  Fig.  198. 

It  is  obvious  that,  instead  of  increasing  the  throw  of 
the  main  eccentric  in  order  to  effect  the  cut-off  at  differ- 
ent points  of  the  piston  stroke,  we  may  employ  sepa- 


OF  THE 

[•UNIVERSITY; 


134 


JfOD-ERN  STEAM  ENGINES. 


rate  cut-off  blocks  and  move  them  apart  by  a  right  and 
left  hand  screw  S  S,  Fig.  207, -giving  an  example  of 
the  arrangement.  The  distance  the  cut-off  blocks  must 
be  moved,  in  this  case,  in  order  to  vary  the  point  of 
cut-off  to  any  given  amount,  may  be  found  by  the  con. 
struction  in  Figs.  181  and  182,  the  amount  the  cut-off 
valves  must  bo  moved  exactly  equalling  the  amount  of 
increased  travel  the  main  valve  must  have  to  cut-off  at 
any  point  earlier  than  the  longest  point  of  cut-off. 

It  is  better,  however,  to  effect  the  earlier  points  of 
cut-off  by  increasing  the  main  valve  travel  than  it  is  to 
move  the  cut-off  valves,  because  a  more  free  admission 
of  steam  is  given.  Suppose,  for  example,  that  the 
valve,  in  Fig.  198,  had  cut-off  valves  adjustable  by  a 
screw,  as  in  Fig.  208,  and  that  the  cut-off  eccei.tric 
being  set  to  cut-off  at  the  same  time  as  the  main  valve, 
we  move  the  cut-off  valve  £  inch  (by  means  of  the 
screw)  wider  apart  so  as  to  effect  the  cut-off  at  half- 
stroke,  and  the  port  openings  will  be  as  in  Fig.  209, 
which,  on  comparison  with  Fig.  203  for  the  cut-off  at 
half-stroke  by  means  of  increasing  the  main  valve 

•a  3* 


1 

1 

\ 

\ 

/ 

/ 

f\ 

\ 

\ 

Fig.  210. 

travel  (all  the  other  elements  being  alike  for  the  two 
cases),  shows  the  steam  admission  to  be  more  tardy  and 
the  cut-off  less  sharp.  Fig.  2 1 0  gives  the  port  openings 
with  the  cut-off  valves  adjusted  to  cut  off  at  quarter- 
stroke,  and  compares  very  unfavorably  with  Fig.  205, 
in  which  the  cut-off  was  effected  by  increasing  the  main 
valve  travel,  the  cases  being  identical  in  all  other  re- 
spects, that  is  to  say  the  dimensions  of  valve  ports,  etc., 
are  alike  in  the  two  cases. 

Fig.  2 1 1  represents  a  cut-off  valve,  which  operates 
on  a  fixed  seat  in  a  steam  chest  divided  into  two 
compartments,  a  and  b.  It  is  obvious  that,  in  this  class 
of  valve,  the  steam  that  surrounds  the  main  valve  in 


the  lower  compartment  I  of  the  chest,  is  not  affected 
by  the  cut-off  and  acts  to  maintain  the- pressure  of  the 
steam  in  the  cylinder  after  the  point  of  cut-off,  hence 


/// //////  /////////r//A 


^^S> 


•7     rp^s       x^.-^v. K>."V 

£^^^^^^E 


W7////7ft 


Fig.  211. 


\y//7//7///\ 


it  is  desirable  to  keep  the  size  of  the  lower  compart- 
ment as  small  as  possible,  and  thus  limit  its  cubical 
contents. 

Tn  this  design  of  valve  gear,  the  longest    point    of 
cut-off     is    obtained  by   the  shortest  amount  of  valve 


Fig.  212. 

travel,  and  if  the  ports  in  the  cut-off  valve  are  of  the 
same  width  as  those  in  its  seat,  the  least  amount  of 
travel  that  will  effect  the  cut-off,  is  that  equal  to  twice 
the  width  of  the  ports.  The  two  .extreme  positions  of 
the  valve  are  shown  in  Fig.  212,  these  being  the 
positions  at  their  respective  points  of  cut-off  for  the 
two  piston  strokes,  and  it  is  seen  that  the  valve,  moving 
from  its  position  in  the  upper  to  that  in  the  lower  half 
of  the  figure,  has  traveled  a  distance  equal  to  twice  the 
width  of  the  port. 

The  useful  range  of  this  form  of  valve,  is  limited 
by  reason  of  the  extreme  amount  of  wire  drawing  of 
the  steam  that  occurs  if  it  is  attempted  to  cut-off  steam 
at  late  points  in  the  piston  stroke,  and  the  design  is 
therefore,  useful  for  the  earlier  points  of  cut-off  only, 
as  from  quarter  to  half-stroke. 


i;tl>l\<;    CUT-OFF    VALVES. 


135 


TO    FIND    T1IK    LIMITS   <>K    T11K    HAMiK  OK    (TT-eKK. 

•••   latest  ]••  .t-off  being  given  to 

fun!  the<-ari:e>t   [M.inl    at   which    tin-  valve  can   clTrct   the 

cut-off,  the  amount  thevalvi  i.crea.-ed. 

and  thr  position  for   the  cut-off  eccentric,  \vc  proceed  as 
in  Fig.  1M.".,   in   which   tin-   inner  circle  I!  I>   repn 
the  .-honest  amount  of  'valve  i  rave!  (iis  diameter  equal- 
Ling  twice  the  width  of  the  ports),  and  T  the  position  of 
the  .Tank    at    the   late.-:  cut-off.  S    represents  a 

]iortion  of  the  \alve  seat  containing  one  port  (whir 

all  that  is  in>ce.-sary  .-ince  tin;  openings  at    all   the   ports 
in  tin-  seat  will  lie  alike),  and    V    represents  a  portion  of 


and  the  shortest   val\c  stroke,  from   tl. 

their  positions  Cor   tin;  ,-horlesl    point  of   cut  olT  and  the 

:d\  e  stroke  as  follows: 

The  crank  being  on  its  dead  center  13;  the  cut-off 
eccentric  at  n:  and  the  edge  of  the  valve  at  <l  when 
tho  parts  are  set  in  the  position  necessary  for  the 
shortest  cut-off,  the  question  is,  how  much  we  must 
lengthen  the  valve  stroke  in  order  to  enable  the  valve 
to  cut-off  as  early  as  possible,  and  to  find  this,  we  mark 
a  dotted  line  /,  distant  from  edge  e  of  tho  port  to  the 
amount  tin-  port  must,  l.e  open  for  the  lead  when  the 
crank  is  at  1!.  We  then  take  the  distance  ,//,  and  mark 
from  n  the  point  g,  and  draw  line  g  g,  we  then  prolong 


Fiy.  213. 


the  valve  containing  one  port.  Now,  it  is  clear  that  the 
c;ii-o:I  eccentric  must  stand  as  much  behind  the  dead 
center  1!  as  the  crank  stands  ahead  of  it  when  the  cut- 
off occurs,  hence  we  take  the  radius  B  T,  and  from  B 
mark,  at  »,  the  position  (if  the  cut-off  eccentric  when 
the  crank  is  at  B,  and  it  follows  that  while  the  crank 
moves  from  B  to  T,  the  cut-off  eccentric  will  move  from 
n  to  B,  effecting  the  cut-off  when  it  arrives  at  B,  at 
which  time  edge  a  of  the  valve  will  lie  fair  with  edge  b 
of  the  port.  To  find  the  position  of  the  valve  when 
the  crank  is  at  B  and  the  cut-off  eccentric  at  n,  we 
mark  line  n  n'  and  take  the  radius  C  n;  with  this 
radius,  and  from  edge  b  of  the  port,  mark  edge  d  of 
the  valve,  it  being  clear  that  edge  d  of  the  valve  must 
be  as  far  from  its  mid-position  b  (when  the  valve  is  in 
mid-position,  edges  d  and  b  coincide)as  n'  is  distant  from 
C.  From  d  mark  off  edge  a  of  the  valve  equal  to  the 
width  of  the  port  in  the  seat.  We  have  thus  f  mud  the 
positions  of  the  parts  for  the  longest  point  of  cut-off 


n  by  a  dotted  line  J,  cutting  g  g  at  K,  and  through  K 
we  draw  a  circle  P,  representing  the  path  of  the  cut-off 
eccentric  when  set  for  the  shortest  point  of  cut-off. 
We  have  thus  increased  the  throw  of  the  eccentric  to 
the  amount  n  K,  and,  by  doing  so,  moved  the  edge  of 
the  valve  from  d  to  f,  leaving  the  port  open  to  the 
amount  ef,  which  is  necessary  for  the  lead,  which  will 
obviously  equal  as  many  times  the  opening  e  /as  there 
are  ports  in  the  cut  off  valve. 

Having  found  the  path  of  the  eccentric  for  the  short- 
est cut-off,  we  find  the  position  of  the  crank  at  the 
shortest  point  of  cut-off  by  taking  the  arc,  or  radius, 
K  G  and  mark  it  from  P,  thus  getting  at  H'  the  required 
crank  position  at  the  shortest  point  at  which  it  can  cut 
off  and  leave  the  valve  open  to  the  amount  e  f  of  the 
lead. 

In  Fig.  214,  we  have  a  diagram  of  the  port  openings 
for  the  longest,  and  in  Fig.  215  a  diagram  of  the  port 
openings  for  the  shortest,  points  of  cut-off  found  by  the 


130 


MOJJl-:i!N  KTEAM  ENGINES. 


diagram    Fig.    213,  and  it  is   seen   that,    in  the  latest 
point  of   cut-off,    the  steam    is   extremely  wire-drawn, 

/6 


/ 

x 

\ 

\ 

/ 

r 

--«. 

^ 

N 

s 

/ 

\ 

\ 

/ 

/ 

\ 

,^— 

^ 

' 

x 

K 

V 

N. 

•*». 

J6    it  12  lo  <}  f 

Fi,j.  2 14. 
which  occurs  because  as  the  cut-off  eccentric  approaches 


/ 

/ 

\ 

/ 

r 

k 

N 

\ 

" 

\ 

/ 

Fi(j.  2 1 5. 
the  point  B,  it  necessarily  moves  the  valve  very  slowly, 


We  may,  to  a  certain  extent,  improve  the  admission, 
and  prevent  the  wire-drawing,  by  making  the  cut-off 
valve  ports  wider  than  the  port  in  its  seat,  and  setting 
the  cut-off  eccentric  to  correspond.  Thus,  in  Fig.  2 1 (j, 
the  cut-off  valve  ports  are  ]  inch  wide  and  the  seat 
ports  are  £  inch  wide.  The  least  amount  of  cut-off 
valve  stroke  is,  therefore,  \^  inches,  or  the  width  of 
the  port  in  the  valve  added  to  the  width  of  port  in  the 
seat. 

The  circle  B  D  represents  the  least  amount  of  valve 
stroke,  and  T  the  crank  at  the  longest  point  of  cut- 
off. AYe  mark  n  (as  far  behind  B  as  T  is  ahead  of  B), 
and  thus  get  the  position  of  the  cut-off  eccentric  when 
the  crank  is  at  I!.  To  find  the  corresponding  position 
of  the  valve,  we  take  the  radius  from  the  point  D  to 
n',  and,  with  this  radius,  mark  from  e  the  edge  d  of 
the  valve,  it  being  obvious  that  when  the  cut-off  eccen- 
tric was  at  D,  edge  d  of  the  valve  was  at  e  and  at  one 
point  of  cut-off,  hence  while  the  cut-off  eccentric 
moved  from  D  to  n'  (or  what  is  the  same  thing  to  n 
since  n'  shows  the  amount  of  linear  motion  caused  by 
the  eccentric  in  moving  D  to  n),  the  valve  edge  d 
moved  from  e  to  its  position  in  the  figure.  Xow  it  is 
clear  that  in  lengthening  the  cut-off  eccentric  throw, 


scarcely  moving  it  at  all  during  the  2  inches  of  piston 
motion  previous  to  the  final  point  of  cut-off. 


Fig.  2 1 6. 

from    n   towards  K,  we  move  the  valve  edge   d   baric 


towards  e,  and  the  utmost  we  can  do  this,  and  still  leave 


CUT-OFF  7ALVES. 


137 


tlio  port  open   for  the  load,  is  the  radius  <l  /:  hence  we 
mark  /.  distant  from  e  to  the  amount  of    lr;id  the  \ 
is  to    lijive.   and    taking  radius   •//  we  mark  from  «'  ilie 
point  •/,  which  gives  the   amount    we  can  push  the  \ 
back    to    lengthen    its   travel     while    still      leaving     it 

'..'.; -4  if 


/" 

\ 

/ 

* 

s 

N 

/ 

\ 

/ 

\ 

\ 

\ 

/ 

1 

• 

— 

—  ; 

=± 

,--" 

\ 
X 

y 

V, 

V, 

Sa 

Fig.  -J17. 

the  amount  e  /  of  lead.  From  ^  we  draw  the  line 
g  g',  and  then  prolong  the  eccentric  throw-line  by  a 
dotted  line  J,  and  through  the  intersection,  at  K,  of  J 
and  </',  we  mark  circle  1'  which  represents  the  path  of 
t  lie  center  of  the  eccentric  when  its  throw  is  increased 
for  the  shortest  point  of  cut-off. 


\ 


\ 


N 


\ 


/Of 
Fig.  218. 

To  find  the  crank  position  at  the  shortest  point  of 
cut-off,  mark  line  B  G  at  a  right  angle  to  B  D,  and 
take  the  arc  K  G  (in  this  case  63°),  and  from  B'  mark 


II',  which  is  the  crank  position  at  the  shortest  point  of 
cutoff,  the  crank  throw-line  being  at  II'  II.  For  the 

•est  point  of  cut-oil  the  valve  will  effect,  we  have, 
then,  the  piston  at  its  dead  center-  I!  ami  the  cut-off 

'itric  at  a,  while  for  the  shortest  point  of  cut-off  we 
have  the  crank  on  its  dead  center  B',  the  cut-off  eccen- 
tric at  K,  and  the  edge  d  of  the  valve  at  e  open  for  the 
lead.  Having  set  the  parts  by  this  construction,  Fig. 
1'I7  shows  the  port  openings  at  the  longest  point  of 
cut-off,  and  it  is  seen  that,  although  the  wire-drawing 
is  less  than  in  Fig.  214,  it  is  still  inadmissably  great 
during  6  inches  previous  to  the  point  of  cut-off.  But 


\ 


Fig.  219. 

we  may  set  the  valve  by  this  construction,  and  not 
employ  it  to  cut-off  at  a  later  point  than  half-stroke, 
the  steam  admission  for  which  is  shown  in  Fig.  218, 
and  it  is  seen,  on  comparison  with  previous  diagrams 
representing  the  port  openings  when  the  cut-off  is  at 
half-stroke,  that  the  steam  supply  is  here  fuller  and  the 
wire-drawing  less.  Lengthening  the  valve  stroke  suf- 
ficient to  effect  the  cut-off  at  quarter-stroke,  we  get  the 
port  openings  shown  in  Fig.  219,  and  here  again  it  will 
be  seen,  on  comparison  with  previous  diagrams,  that 
the  port  opening  is  unusually  wide  and  the  cut-off 
sharp  and,  therefore,  advantageous  in  both  respects. 


CHAPTER    VI. 


VARYING  THE  POINT  OF  CUT-OFF  BY  SHIFTING  THE  ECCENTRIC  ACROSS  THE  CRANK-SHAFT. 


Instead  of  employing  a  separate  cut-off  valve,  the 
points  of  cut-off  may  be  varied  by  employing  a  single 
valve  and  shifting  the  position  (on  the  crank-shaft) 
of  the  eccentric  so  as  to  reduce  its  throw,  and  therefore 
the  travel  of  the  valve.  The  line  in  which  the  eccen- 
tric may  be  moved,  is  shown  as  follows: 

In  Fig.  220  is  shown  an  eccentric  whose  bore  is 
slotted  so  that  it  may  be  shifted  across  the  shaft.  The 
circle  r  represents  the  path  of  the  center  of  the  eccen- 
tric when  moved  to  its  position  of  greatest  throw,  as 
shown  in  the  full  lines,  the  center  of  the  eccentric 
being  at  e.  The  circle  /  represents  the  path  of  the 
center  of  the  eccentric  when  shifted  to  its  position  of 
least  throw,  as  denoted  by  the  dotted  circle  H,  the  center 
of  the  eccentric  being  at  x. 

The  circles  r  and  /  Fig.  221,  correspond  to  circles  r 
and  /  in  Fig.  220,  the  radins  C  x  representing  the  lap 
of  the  valve.  The  vaive  is  shown  to  have  no  lead,  the 
eccentric-rod  R  being  shortened  for  convenience  of 
illustration;  the  crank  is  supposed  to  be  on  its  dead 
center  at  B.  Now  suppose  the  eccentric-rod  R  to  be 
pivoted  on  the  valve,  the  other  end  being  disconnected, 
and  if  we  move  it  across  the  outer  circle  (which  repre- 
sents the  path  of  the  eccentric  center  when  at  its  great- 
est throw)  the  center  of  the  eccentric  strap  bore  will 
138 


move  in  a  path  denoted  by  the  line  from  e  d.  During 
that  part  of  this  line  that  runs  from  e  to  x,  the  throw 
of  the  eccentric  will  be  reduced  and  the  cut-off  has- 
tened, the  engine  running  in  the  direction  denoted 
by  the  arrow,  but  after  the  eccentric  has  passed  the  line 
x,  the  valve  would  be  in  position  for  the  engine  to  run 
in  the  opposite  direction,  its  throw  increasing  as  it  is 
moved  towards  the  point  d.  As  the  valve  and  crank 
have  remained  motionless  while  the  eccentric-rod  was 
moved  across  the  shaft  to  mark  the  line  e  d,  it  is  clear 
that  so  far  as  this  crank  position  (B)  is  concerned,  the 
eccentric  may  be  shifted  to  any  position  between  e  and 
d  without  altering  the  valve  lead. 

Now  suppose  the  engine  to  make  a  half-revolution, 
the  crank  being  on  the  dead  center  D,  as  in  Fig.  222, 
the  port  b  being  about  to  open  for  the  live  steam,  and 
supposing  the  eccentric-rod  to  be  pivoted  to  the  valve 
as  before,  and  the  valve  and  crank  to  remain  at  rest, 
then  the  center  of  the  eccentric-strap,  in  being  moved 
across  the  shaft,  will  move  in  a  path  denoted  by  the 
line  e'  d'  But  while  the  crank  moved  from  B  to  D, 
the  line  e  d,  Fig.  221,  has  moved  to  the  position  shown 
in  Fig.  222,  and  it  becomes  evident  that  the  port  b 
would  be  given  an  amount  of  lead  represented  by  the 
distance  between  e'  and  e.  This  amount  will  obviously 


Hg.  223. 


IS 


139 


140 


MODERN  STEAM  ENGINES. 


diminish  as  the  eccentric  is  shifted  across  the  shaft 
towards  the  position  x  of  least  throw  until,  on  arriving 
at  x,  there  would  be  no  lead  for  either  port,  because  at 
x  the  arcs  c  d  and  e'  il'  coincide. 

It  is  obvious,  however,  that  the  longer  the  eccentric- 
rod  is,  the  nearer  the  arc  e  d  will  approach  to  a  straight 
line,  and  that  if  it  were  a  straight  line  the  distance  e  e' 
would  be  less  and  the  lead  variation  would  also  be  less. 
while,  if  the  eccentric-hanger  was  infinitely  long  so  as 
to  move  the  eccentric-hanger  in  a  straight  line,  the  lead 
would  be  equal  for  the  two  ports. 

The  eccentric  is  also  attached  to  an  arm  or  hanger 
that  swings  on  a  center,  and  it  is  obvious  that  the 
longer  this  hanger  is,  the  nearer  the  arc  c  d  will  be  to  a 
straight  line  and  the  less  the  distance  e  e'  and  the  lead 
variation  will  be. 

For  the  purpose  of  considering  the  lead  variation 
due  to  swinging  the  eccentric  across  the  shaft  in  an  arc 
of  a  circle,  it  is  sufficient  to  suppose  the  eccentric-rod 
and  eccentric-hanger  to  be  of  equal  lengths. 

The  amount  of  lead  variation,  thus  shown  to  accom- 
pany the  shifting  of  the  eccentric  across  the  shaft,  will 
obviously  increase  in  proportion  as  the  range  of  cut-off 
is  increased. 

In  order  to  make  the  lead  variation  show  plainly  in 
the  figures,  the  length  of  the  eccentric-rod  has  been 
taken,  as  equal  to  but  six  times  the  amount  of  the  valve 
travel,  and  as  the  eccentric  hanger  has  been  taken  as 
of  the  same  length,  the  same  radius  serves  for  arc  e  d 
and  e'  d'. 

In  Fig.  223,  the  valve  is  supposed  to  have  lead,  the 
arcs  i]  being  distant  from  circle  /  to  the  amount  of  the 
valve  lead,  and  therefore  distant  from  C  to  the  amount 
of  the  lap  and  the  lead.  With  the  crank  at  B,  the 
eccentric  center,  when  in  its  position  of  greatest  throw, 
will  be  at  t,  and  the  cut-off  will  occur  when  it  has 
arrived  at  d.  This  is  clear,  because  if  we  placed  the 
valve  in  position  at  cut-off,  and  moved  the  strap  end 
of  the  eccentric-rod  across  the  shaft,  its  center  would 
move  in  the  arc  from  /  to  d. 

It  will,  therefore,  be  perceived  that  whatever  position 
the  center  of  the  eccentric  may  be  shifted  to.  between 
the  points  from  e  to  the  line  I  of  centers,  the  cut-off  will 
occur  when  the  eccentric  center  passes  the  line  /  d. 
Similarly  when  the  crank  is  at  D.  and  the  port  b  is  open 


to  the  amount  of  the  lead,  the  eccentric  center  ought  to 
be  (if  the  valve  is  to  have  equal  lead)  at  e',  but  it  will, 
for  reasons  already  explained  with  reference  to  Fig. 
'-'I1'-!,  be  at  e",  hence  the  lead  will  be  greater  for  port  b 
than  for  port  a.  The  cut-off,  however,  will  occur  when 
the  eccentric  center  crosses  the  arc  from /to  d',  this 
arc  being  the  path  that  would  be  described  by  the 
center  of  the  eccentric  strap  if  the  eccentric-rod  was 
pivoted  to  the  valve,  and  its  strap  end  moved  across 
the  shaft.  It  follows,  therefore,  that  the  cut-off  will  be 
later  for  the  stroke  when  the  piston  is  moving  from  the 
head  end  to  the  crank  end,  and  it  is  also  seen  that  as 
the  two  arcs  e'  and  e"  coincide  on  the  line  of  centers, 
therefore  the  lead  will  be  diminished  in  proportion  as 
the  eccentric  is  moved  towards  the  line  of  centers  for 
earlier  cut-offs,  and  will  be  all  taken  up  when  the  eccen- 
tric is  at  its  inner  position  for  the  shortest  cut-off. 

Instead,  however,  of  shifting  the  eccentric  from  a 
pivot  or  pin  situated  on  the  line  of  engine  centers,  we 
may  do  so  from  a  pin  on  a  line  ///  ///.  Fig.  224,  at  an 
angle  to  the  line  of  centers  which  will  reduce  the  valve 
lead  for  the  longest  points  of  cut-off,  and  either  increase 
the  lead  at  the  early  cut-offs  for  both  strokes,  or  for 
the  head  end  port  only,  according  to  the  angle  of  the 
line  in  m  to  the  line  of  centers.  Thus,  in  Fig.  224,  the 
ercenirir  is  supposed  to  be  shifted  across  the  shaft  from 
ft  point  or  pivot  on,  the  line  «  m.  The  arcs  g  g,  have 
a  radius  from  the  center  (1,  equal  to  the  amount  of 
lap  of  the  valve.  The  arc  e  x  is  drawn  with  the  length 
of  the  eccentric-rod  as  a  radius,  and  from  the  center  of 
the  valve,  when  the  latter  is  in  position  ready  to  open 
port  a  for  the  lead,  and,  therefore,  represents  the  path 
in  which  the  eccentric  must  move  across  the  shaft  in 
order  to  maintain  equal  lead  for  all  points  of  cut-off 
on  this  piston  stroke.  But  the  path  in  which  the  eccen- 
tric would  actually  move  (its  point  of  suspension  being 
on  the  line  m)  is  shown  by  the  arc  e'  x',  and  it  is  seen 
whatever  the  amount  of  lead  at  e',  it  will  increase,  as 
the  eccentric  is  shifted  towards  x'  for  the  earlier  cut-offs. 

'i  he  amount  of  difference  in  the  lead  will  obviously 
depend  upon  how  far  distant  the  point  of  eccentric- 
hanger  suspension  is  located  away  from  the  line  of 
engine  centers. 

Turning  now  to  the  stroke  when  the  piston  is  moving 
from  D  to  B,  and  the  port  b  is  taking  steam,  the  arc  e" 


VAVLE  MOTIONS    WITH   SHIFTING    ECCENTRIC. 


Ill 


lieing   striu-k    from   the   lint1    <>f    center:-    /  of  the 
lie.  iiml  with  a  radius.  ci[ual  to  tin-  Inn  the 

center  of  [he  cylii.  to   the  center   of  the  crank- 

shaft  is,    as    in    ]•>.  a    line    parallel   to 

which  the    eccentric    must  move    in    order  to    keep    the 


drawn,  this  U'ing   the   arc  on    whicli   tlie  eccentric   will 
actually  move  when  shifted    aCTOM    the  shaft.  as  may  be 
follows: 


the  crank  to  be  at  D,  and  the  point  of  eccen- 
tric suspension  to  be  on  the  line  m  to  the  left  of  the 


lead  equal  on  this  stroke  for  all  points  of  cut-oS.  To 
find  the  line  in  which  it  will  actually  move,  the  line  m 
m  must  be  prolonged  to  the  left  hand  of  the  figure,  and 


Fig.  ?>'•>. 

from  a  point  on  this  line,  and  with  the  length  of  the 
eccentric-hanger   as  a  radius,  the   arc   e'"  x'"  may   be 


%.   224. 

figure,  and  if  a  pencil  be  inserted  in  the  center  of  the 
eccentric  and  the  eccentric-hanger  were  operated  by 
hand,  then  the  pencil  point  would  mark  or  describe  the 
arc  e"'  x'".  For  this  stroke,  therefore,  the  amount  to 
which  the  lead  will  vary  as  the  eccentric  is  moved  from 
its  outermost  to  its  innermost  position  is  that  repre- 
sented by  the  difference  of  the  distance  between  e"  and 
e'"  and  x"  and  x'".  The  variation  in  the  amount  of 
the  lead,  for  the  two  ports,  is  shown,  for  the  longest 
point  of  cut-off,  by  the  difference  in  distance  between 
the  points  e  and  e'  and  that  between  e"  and  e'", 
while,  for  the  shortest  points  of  cut-off,  it  is  shown  by 
the  difference  between  the  points  x  x'  and  x"  x'". 

TO    FIND    THE    PISTON    POSITION    FOR    A    GIVEN    ECCK.V- 
TH1C    1'OSITION. 

In  Fig.  225,  the  arc  /  has  a  radius  equal  to  the  lap 
of  the  valve,  and  circle  g  a  radius  equal  to  the  lap  and 
the  lead,  and  it  follows,  from  what  has  already  been 
explained,  that  with  the  crank  at  B,  and  the  valve  open 
to  the  amount  of  the  lead,  the  eccentric,  when  at  its 
greatest  throw,  will  be  at  e,  and  the  cut-off  will  occur 
when  it  arrives  at  d.  As  the  crank  will  move  through 


MODERN  STEAM  ENGINES, 


the  same  number  of  degrees  of  arc  that  the  eccentric 
does,  we  may  set  the  compasses  to  radius  e  d,  and  mark, 
from  B,  the  position  H  of  the  crank  at  the  point  of 
cut-off.  To  find  the  corresponding  piston  position,  we 
set  a  pair  pf  compasses  to  represent  the  length  of  the 
connecting-rod  on  the  same  scale  that  the  outer  circle  B 
D  represents  the  patli  of  the  crank-pin,  and  from  a 
point  on  the  line  of  centers  I  I  of  the  engine,  mark 
from  H  an  arc,  giving  at  s  the  position  of  the  piston  at 
the  point  of  cut-off.  Suppose,  for  example,  the  engine 
stroke  was  24  inches,  and  the  outer  circle  r  being  3 
inches  will  represent  the  path  of  the  crank-pin  on  a 
scale  of  -J  full  size,  or  £  inch  per  inch.  Supposing  the 
connecting-rod  to  bear  the  ordinary  proportion  of  three 
times  the  length  of  the  piston  stroke,  and  its  length 
will  be  72  inches,  hence  the  radius  of  the  arc  H  s  will 
be  72  eighths  of  an  inch,  or  9  inches.  Then  as  the  dis- 
tance from  B  to  s  is  1 J  inches,  we  multiply  this  by  cS 
and  get  15  inches  as  the  piston  position  at  the  point  of 
cut-off. 

If  now  the  eccentric  be  moved  to  position  v,  its 
path  will  be  on  the  circle  u  and  the  cut-off  will  occur 
.  when  the  eccentric  arrives  at  t,  because  at  that  time  the 
valve  will  be  moved  from  its  mid-position  to  an  amount 
equal  to  the  amount  of  the  steam -lap;  hence  the  arc 
moved  through  by  the  eccentric  from  the  beginning  of 
the  piston  stroke  to  the  point  of  cut-off,  is  the  arc  v  t. 
To  find  the  position  of  the  crank  at  the  point  of  cut-off, 
we  take  the  radius  v  t,  and  from  B',  on  circle  u  at  the 
line  of  centers,  mark  an  arc  G.  A  line  from  the  center 
C,  and  cutting  the  point  of  intersection  of  arc  G  with 
circle  u,  gives  at  h  the  position  of  the  crank  at  the 
point  of  cut-off.  An  arc  whose  radius  represents  the 
length  of  the  connecting-rod,  and  whose  center  is  on 
the  line  of  engine  centers,  gives  at  TO  the  position  of  the 
piston  at  the  point  pi  cut-off. 

If  the  eccentric  be  moved  further  across  the  shaft 
to  the  position  represented  by  M,  the  path  of  its  center 
will  be  on  the  circle  y,  and  to  find  the  position  of  the 
crank  when  the  cut-off  occurs,  we  take  the  radius  w  n, 
and  from  B",  where  circle  y  crosses  the  line  of  centers, 
mark  an  arc  J,  and  a  line  from  C,  passing  through  the 
intersection  of  J  with  circle  y,  gives,  at  h',  the  crank 
position  at  the  time  the  cut-off  occurs,  while  the  arc 
from  /i'  gives,  at  p,  the  corresponding  piston  position. 


We  have  now  to  consider  the  earliest  point  at  which 
the  cut-off  can  be  effected,  hence  let  it  be  supposed  that 
the  eccentric  center  is  moved  to  position  x,  a,nd  the 
crank  being  on  its  dead  center  at  B,  the  port  will  be 
open  to  the  amount  of  the  lead,  and  as  the  cut-off  will 
occur  when  the  eccentric  reaches  x',  we  take  the  radius 
x  x'  and  mark  it  from  B'",  obtaining,  by  the  same  lines 
as  before,  the  crank  position  h".  Tt  is  obvious,  how- 
ever, that  if  the  valve  had  no  lead,  there  would  be  no 
admission,  because  when  the  crank  was  on  its  dead 
center  B,  the  port  would  be  blind,  and  as  soon  as  the 
crank  moved,  the  valve  would  move  back  further  over 
the  port. 


TO    FIND    THE    AMOUNT    OF    STEAM    PORT    OPENING    FOR 
EACH    POINT    OF    CUT-OFF. 

In  Fig.  226,  the  outer  circle  represents  the  path  of 
the  eccentric  center  when  at  its  greatest  throw,  while 
the  circle//  has  a  radius  equal  to  the  steam  lap  i>f  the 
valve.  Now,  suppose  the  path  of  the  eccentric  •seiuer 


Fig,  226. 

to  be  on  the  circle  r  r,  and  when  it  is  at  e,  the  valve  will 
have  moved  from  its  mid-position  to  the  amount  or  dis- 
tance C  x,  the  point  x  will,  therefore,  represent  the 
edge  of  the  steam  port  and  the  edge  of  the  valve  when 
the  eccentric  is  at  e.  While  the  eccentric  is  moving 
from  e  to  D,  it  is  opening  the  port,  hence  the  maximum 
amount  of  port  opening  may  be  measured  from  x  to 


VALVE   .l/./yyo.Y.v    W/77/    >7///-77.\v;    ECCENTRIC. 


143 


f>.     Tf  the  valve,  has  no  ovcrtravel.  rlic  maximum  )x>rt 
!i:ng  will  l,c'  tin-,  radius  from  r  ID  I),  when  tin-  ecci-n- 
i  the  circlr  r  r.      Mm  suppose  the  BOO 

path    to    1 11    the    circle    n    >i.  then    the    maximum    of 

steam  p  >rt  opening  will  be  equal  to  the  radius  .1  /.• ;  or, 
if  the  eccentric-path  he  on  circle  /,  then  the  maximum 
amount  of  steam  port  opening  will  In-  represented  by 
the  radius  ./•  ;/.  The  area,  of  pott  opening  will  obviously 
<lepcn<l  upon  the  dimensions  of  the  ports  and  upon 
whether  the  valve  is  double  or  single  ported. 

TIIK    POINT    OF    ADMISSION. 

If  th'  .id,  the  admission  occurs  when 

the  crank   passes  the  dead  center,  but  if  the   valve 
lead,  tin:   point  of  admission  may   l>e  found  as  follows: 

In  Fig.  221.  the  outer  circle  represents  the  path  of 
the  crank-pin  and  that  of  the  eccentric  as  before, 
•le/  has  a  radius  equal  to  the  amount  of  valve  lap, 
and  circle  g  a  radius  equal  to  the  lap  and  the  lead. 
\Vhen  the  crank  is  at  B,  and  the  valve  open  to  the 
amount  of  the  lend,  the  eccentric,  when  set  for  the 
latest  rut -off.  will  be  at  e,  and  as  the  cut-off  will  occur 
when  it  reaches  point  •/.  then-fore  the  arc  it  moves 
through,  while  the  crank  moves  from  the  dead  center 
R  to  the  point  of  cut-off,  is  the  length  of  the  arc  e  d, 
hence  we  take  this  distance,  and  from  n  (where  the 
utric  will  lie  when  admission  occurs)  mark  arc  A, 
ainl  a  line  A',  drawn  from  the  intersection  of  A  to  the 
center  C,  represents  the  crank-pin  position  at  the  point 
of  admission  for  the  latest  point  of  cut-off. 

Now  suppose  the  eccentric  to  be  moved  to  e'  for  the 


:'.   and    the    length  of    arc,  it  will    move 
-olT.  is   from  v  to  d',  and 

as  it  will  move  through   half  this   arc,  or  from  v  to  e', 

o  the  amount  of  the  lead,  and 

•  •:•  half   v.  ng    it.  \\ e  take  the  radius  e'  d' 

I  re  circle  g  cuts  the 

line  of  centers,  mark  area  .1  and  K,  and  then  draw  lines 

H  C  and  a  C,  and  line   ,/  ( '  will  be  the  crank  position 


Fi'j.  22-. 

at  the  point  of  admission,  while  II  C  will  be  its  position 
at  the  point  of  cut-off. 

This  is  clear  because  arc  v  c'  equals  arc  E  J,-  and  arc 
E  F  equals  arc  >•'  </'. 

It  is  seen,  therefore,  that  if  the  valve  is  given  lead, 
then  in  proportion  as  the  eccentric  is  moved  across  the 
shaft  for  the  earlier  points  of  cut-off,  the  point  of 

admission  is  hastened: 
* 


OALIF< 


CHAPTER.     VII. 


EXAMPLES  FROM  PRACTICE. — AUTOMATIC    CUT-OFF  ENGINES. 


Automatic  Cut-off  Engines  may  be  divided  into  two 
classes,  as  follows:  Those  in  which  the  valve  is  released 
from  its  operating  mechanism  when  closing  to  effect  the 
cut-off,  which  is  done  to  accelerate  its  movement,  and 
those  in  which  its  action  is  positive  throughout. 

The  Automatic  Cut-off  Engine  possesses  the  follow- 
ing advantages. 

1st.  It  contains,  within  itself,  means  of  altering  the 
amount  of  its  power  to  suit  changes  in  the  amount  of 
its  load  or  duty,  while  permitting  the  steam  to  flow 
unchecked  from  the  boiler  to  the  steam  chest. 

'•>iul.  It  contains,  within  itself,  means  of  maintaining 
a  constant  proportion  between  its  piston  power,  and  the 
load  it  drives,  notwithstanding  ordinary  fluctuations  of 
boiler  pressure,  and  it  does  this  without  checking  the 
flow  of  steam  from  the  boiler  to  the  steam  chest. 

3rd.  It  accomplishes  both  the  above  named  results 
by  varying  the  amount  of  expansion,  and,  therefore, 
avoids  the  loss  that  accompanies  their  accomplishment 
by  means  of  wire-drawing  the  steam. 

4th.  It  adjusts  its  power  to  the  load  more  quickly 
than  is  possible  by  means  of  varying  the  steam  chest 
pressure,  as  is  done  when  a  throttling  governor  is  used, 
and  thus  maintains  the  engine  speed  more  uniform. 

5th.     It  possesses  all  the  qualifications  of    an  engine 

having  a  fixed   point   of    cut-off,  because   if    the    load 

remains  constant,  it  retains  the  point  of    cut-off   at   a 

fixed  point  in  the  stroke,  and   only  varies  the  point  of 

144 


cut-off  when  the  conditions  of  a  varying  load  demand 
it. 

When  an  engine  has  a  fixed  point  of  cut-off,  and  the 
engine  speed  is  regulated  by  varying  the  pressure  at 
which  the  steam  from  the  boiler  is  admitted  into  the 
steam  chest,  three  evils  are  induced: 

First,  suppose  the  engine  to  bo  running  at  its  normal 
speed  and  a  sudden  decrease  occurs  in  its  load,  and  the 
engine  speed  will  increase,  causing  the  speed  of  the 
governor  to  increase  and  check  the  flow  of  steam  into 
the  steam  chest;  but  the  steam  chest  will,  at  this  time, 
be  filled  with  steam  admitted  to  it  before  the  governor 
checked  the  inflowing  steam,  hence  the  steam  in  the 
steam  chest  forms  a  reservoir  acting  in  opposition  to 
the  governor,  and  this  obviously  prolongs  the  time 
necessary  to  bring  the  engine  power  down  to  meet  the 
requirement  of  a  reduced  load,  and  it  follows  that  the 
engine  speed  will  fluctuate  because  of  the  sluggishness 
of  the  method  of  governing  it. 

Secondly,  suppose  the  engine  to  be  running  at  its 
normal  or  proper  speed,  and  that  its  load  suddenly 
increases,  and  its  speed  will  decrease,  causing  the  gover- 
nor to  increase  the  flow  of  steam  into  the  steam  chest, 
but  the  inflowing  steam  will  be  partly  expanded  in  rais- 
ing the  pressure  of  the  steam  already  in  the  steam 
chest,  and  the  latter,  therefore,  acts,  to  a  certain  extent. 
in  opposition  to  the  governor,  and,  therefore,  delays  its 
action  in  governing  the  engine  speed.  In  either  case, 


7V//-:  r»im-:i;-M.Li-:x  ENGINE. 


145 


therefore,    tli.  ii   amount   of 

tween  i '  ind    its  effect   upon 

the  engine  >]»•(•(!. 

Tiir    lliinl    evil  is   thai  a     throttling    engine,    with    a 

fixed     ]Kiiiit     of      cut-olf.    must     either    wiredraw     the 

ii    considerably    or   else    he   deficient    in    jroveriiing 

jxiwcr  uiiilcr  llie  changes  that   are   liable  t -cur  in  the 

holler    pressure.        Thus,     suppose    the    holler    pressure    to 

he  at   its  lowest  ] lennissil ile  [mint,  ainl  the   governor  will 

i    the    Men  m    pipe    to  iis    wide-l.  ami    if    this    is    slill'l- 

c-ieiit    to    maintain    the   engine    speed,    then    when    the 

holler    pressure    il  highest     point,  the    governor 

must  close  ihe  steam  ]iipe    sullieiently  to    keep  the  steam 

MI    to   what    it  was   umler   the    lowest 

hoiler    pressure,    hence    supposing    the    amount    of     the 
engine  load    t..   remain  then  the    wire-drawing 

acti'  -nor  must,  at   Ii  i!    the  greale-l 

amount  of   fluctuation  that   may  occur  helweeiithe  high- 
est and  lowest   hoiler  pre.-suiv>. 

THK     rOKTKII  -AI.I.KN     KMJIXK. 

The  I'oi'ter-Alleii  was  the  pioneer  in  high  piston 
stationary    engines,  and    has  attained  a    piston   speed   as 
high  ;LS    1,100    feet    per   minute,  without,   noise  or  shock. 

Its  usual  piston  speed,  however,  is  from  ahollt  ll'iii  to 
S.'iO  teet  per  minute. 

prominent   features  in  tln>  design  are  as  follows  : 

1st.  The  valve  motion  is  so  designed  as  to  proportion 
the  steam  admission  and  supply  to  the  piston  velocity, 
and  thereby  act  to  counterhalance  the  reciprocating 
parts  of  the  engine. 

•Jnd.  The'  valves  are  so  constructed  and  operated  as 
to  give  a  rapid  opening  and  steam  supply  early  in  the 
stroke,  and  a  quick  cut-off,  while  their  amount  of  travel 
is  limited  and  their  speeds  diminished  during  that  part 
of  the  travel  in  which  lap  of  the  valvfe  is  being  taken 
up. 

3rd.  The  variation  in  the  point  of  cut-off  is  effected 
by  means  of  altering  the  amount  of  valve  travel,  which 
the  mechanism  of  the  engine  effects  automatically. 
This  variation  is  governed  by  the  amount  of  resistance 
of  the  load  or  duty  of  the  engine,  the  point  of  cut-off 
occurring  later  in  the  piston  stroke  in  proportion  as  the 
load  or  dutv  is  increased. 


4th.     A    I  ''iitric   and   link    operates   the    tw  > 

steam  and    t  u  o   exhaust   vahes.  yet    the    exhaust    Valves 
are  actuated  independent Iv  of   the  steam  va 

">lh.  The  valves  are  balanced  to  relieve  them  of  undue 
pressure  to  their  seats,  thus  causing  a  minimum  of 
friction  and  wear,  and  may  he  set  up.  as  occasion  may 
require,  to  a  proper  adjustment  to  their  seals. 

Fig.  L'L'S    is   side    view  of  the   engine,  from    the   con- 
necting rod   Mde.  and    Fig.    rj!)   an   outline   view  of  the 
engine,  from    the   link   side,  and    having  a  part  of    the 
heel     broken   out    to    expose  to  view    the    arrangement 
6  valve  rods. 

The  eccentric  E   operates  the  link  L,  which  is  p 
to  a    pin  a  at  the  top  of  the  arm  A.  which  is   pivoted  at 
•  \er  end  t  by  a  pill  in  the  bracket,  N. 

In  the  slot  •>•  of  the  link  is  the  usual  sliding  block,  to 
which  is  pivoted  the  rod  1,'.  operating  the  wrist  motion 
at  \V.  This  wrist  motion  consists  of  a  three  armed 
lever,  the  lower  arm  receiving  motion  from  rod  R,  the 
upper  arm  operating  the  rod  C  for  the  slide  valve 
spindle  !•'.  and  the  lower  one  operating  rod  D  for  the 
other  slide  valve,  whose  spindle  ia  seen  at  K.  The 
exhaust  valves  are  driven  from  the  top  of  the  link  by 
the  rod  X  which  vibrates  arm  //.  whose  shaft  passes  to 
the  other  side  of  the  engine  and  operates  an  arm,  to 
which  is  attached  a  rod  Z,  which  is  seen  in  the  side 
view.  Fig.  •_>'J!i. 

The  exhaust  valves  are  in  the  same  plane,  and  are 

ated    by    the  same   rod,   but  the  steam  port  slide 

valves  are  not  in  the  same  piano,  the  crank  end   valve 

being  higher  than  the  head  end  valve,  as  is  denoted   by 

the  cover  11  being  higher  than  cover  J. 

The  motion  of  the  link  and  valve  mechanism,  will  be 
fully  explained  hereafter,  it  being  sufficient  for  the 
present  to  point  out  that,  as  the  top  of  the  link  has  more 
motion  than  its  point  of  suspension  on  arm  A,  therefore 
the  valve  has  most  travel  when  the  link-block  is  at  the 
top  of  the  link  slot  /,  in  which  position  it  is  shown  in 
the  engraving. 

To  the  valve  rod  R  (which,  carries  the  link-block),  is 
pivoted  the  rod  G,  which  is  in  turn  pivoted  to  the 
weighted  lever  P.  whose  ball  weight  counterbalances  the 
weight  of  the  rods  G  and  R  and  of  the  link-block. 
The  lever  P  is  actuated  by  the  governor  as  follows: 

AVhen  the  load  or  duty  of  the  engine  is  lightened, 


&    (3)0© 

X          <g 

3)     ®0@o@ 


Til /•:  r»i; TI:H  M.I. i-:\  /; A  ' / /.v /•:. 


147 


the  governor  causes  tho  ball   end   of    lever  1'  to  r.  iwer  of  the  engine  to  a  lightening  of  the 

its   outer  end  depressing  the   rod  •  ;,   which,  therefore,  j  engine  load.     The  point  of  cut-off  is  varied,  in  ordinary 


Side  Elevation..  Fig.  230.  /-.'»</  K/,  ,•„/;,„,. 

The  Link  and  its  Connections. 


r 


Fig.  231. 

The  Wrist  Motion. 


moves  the  link-block  down  the  link-slot  .«,  diminishing 
the  valve  travel  and  hastening  the  cut-off,  so  as  to  con- 
19 


Porter- Allen  engines,  between  the  limits  of  from  quar- 
ter-stroke to  half-stroke,  but  in  engines,  such  as  those 


MS 


MODERN  STEAM  ENGINES. 


for  iron-roiling  mills,  where  occasion  may  call  for  greater 
power,  the  limit  is  extended  between  \  and  ^  stroke. 


THE    CYl.IMlKli    AMI    VALVES. 

The  details  of  construction  arcrinoro  fully  soon  in  the 
following  figures:  Fig.  '-'ISO  gives  a  side  and  end  view 
of  the  eccentric,  the  link  and  the  link  supporting  arm 
A.  The  eccentric  is  formed  solid  with  the  main  shaft. 
and  the  link  solid  with  one  half  of  the  eccentric-strap. 


head  end  of  the  cylinder.  T  and  D  are  the  rods  for 
the  respective  steam  valve  spindles.  The  letters  of  ref- 
erence correspond  to  those  in  the  figures  illustrating 
the  valve  mechanism. 

In  Fig.  2.'!2.  the  cylinder  is  shown  cut  in  half  hori- 
zontally and  viewed  from  above.  The  spindle  F  oper- 
ates the  valve  at  the  crank  end  of  the  cylinder,  and 
through  this  valve  passes  the  spindle  K  for  operating 
the  valve  at  the  head  end.  Fpindle  M  is  for  the  ex- 
haust valves,  these  letters  of  reference  corresponding  to 
those  given  in  the  outline  view,  Fig.  229. 


Horizontal  Section  through  the  Cylinder  and  Valves. 


The  link  is  slotted  so  that  the  valve  rods  pass  centrally 
through  it,  as  shown  in  the  end  view.  The  arm  A  sup- 
ports the  link  on  both  sides,  and  has  provision,  by 
means  of  key  K  and  set  screw  S,  for  adjusting  the 
height  of  the  pins  by  which  the  link  is  pivoted,  this 
being  necessary  to  effect  a  proper  adjustment  so  as  to 
equalize  the  lead  and  the  points  of  cut-off,  as  will  be 
explained  hereafter. 

The  wrist  motion  is  shown  in  Fig.  231,  R  being  the 
rod  from  the  link  block,  d  the  arm  for  operating  the 
valve  at  the  crank  end,  and  e  that  for  the  valve  at  the 


A  cross  sectional  view  of  the  head  end  of  the  cylin- 
der is  shown  in  Fig.  2!!!!,  and  referring  to  these  two 
views,  it  is  seen  that  when  the  steam  valve  opens  the 
port  for  the  admission  of  steam,  the  steam  passes 
through  four  different  openings,  as  denoted  by  the 
arrows. 

The  method  of  relieving  the  steam  valves  from  undue 
pressure  to  their  seats  is  as  follows:  At  m  and  n,  Fig. 
233,  are  two  inclined  planes  at  an  equal  angle  to  the 
valve  face,  and  at  the  back  of  the  valve  is  a  pressure 
plate  P.  fitting  up  to  these  inclined  planes.  The  valve 


Tin-: 


works    l.eiwe,  plate    I', 

u,,,!  r,  !'\-  means  uf   whicli 

it  may    ;  -    that   raisin- 


233. 

Vertical  Secton  through  the  Cylinder  aud  Valves. 

Jilatt'  P  moves  it  away  from,  \\hile    lowering  it  CftUBee    it 

•i[>ro;ii-h  tlie   l>ack    face  of   the    valve    until,  on  meet- 


Sectional  view. 


Fi<j.    234.          Side  view. 
The  Admission  Valve. 

ing  that  face,  the  steam  is  excluded  and  the  valve  re- 
lieved of  the  steam  pressure. 


<»^n 


149 

XTNIVERSI7 

The  strain  valves   ;uv    rcctai>'_nilnr    frames.  Mich  AS  in 
Fi.ir.  I':'.  I,  li:e    n  It   the    valve   at  tin 

:M_:   to  lnil)   A,    wlii 

siiimlle  I'm-  tin'  lu-ail  cnil  valve  passes  through  tin-  hub  // 
which  is  in  lino  with  tin-  center  of  the  latter  valve.  In 
the  s.-cliuiial  view  the  valve  is  shown  in  its  mill-position. 


/•»/.   235. 


Fly.   2.10. 


Fiy.  237. 


sr? 


Various  Positions  of  the  Admission  Valve. 

The  full  effective  widili  of  tlie  port  is  the  width  at  a, 
it  being  obvious  that  the  width  of  the  mouth  of  the 
port  is,  from  the  point  of  admission  until  the  point  of 
cut  off,  covered  by  the  thickness  of  the  metal  at  c,  Fig. 
'!?>'>.  Tlie  valve  length  at  /  is  proportioned  that  when 


150 


MODI-:i!\'  WKAM  ENGINES. 


the  port  opens  on  one  end  as  denoted  by  the  arrows  i 
and  g,  it  will  also  open  at  the  other,  as  denoted  by  the 
arrows  )•  and  s. 

In  Fig.  236,  the  valve  is  shown  at  one  end  of  its 
travel  for  cut-off  at  half-stroke,  and  in  Fig.  I','!",  it  is 
shown  in  position  at  the  other  end  of  its  travel,  and 
about  to  reverse  its  motion. 

The  wear  on  the  valve  and  its  seat,  and  on  the  face 
in  of  the  cover  plate  X,  is  equalized,  because  the 
metal  at  each  end,  c  v  of  the  valve,  passes  entirely 


lias  not  moved  £  inch.  This  is  shown  in  Fig.  238,  in 
which  the  valve  is  shown  at  one  end  of  its  shortest 
travel,  and  it  is  seen  that  it  still  moves  up  to  the  shoul- 
der e  of  the  valve  face,  and  to  the  end  y  of  the  plate  X. 


THE    ACTION    OF    THE    VALVE    MECHANISM. 

Fig.  239  shows  the  position  of  the  parts  when  the 
crank-pin    is   on    its    dead  center  D.     The  rod    R,    is 


D 
O 


Fig.  239. 

Position  of  the  Valve-Motion  at  the  Beginning  of  the  Stroke. 


over  the  surfaces  n  m,  and,  therefore,  prevents  the 
wear  from  forming  a  shoulder,  which  would  occur 
if  the  ends  of  the  valve  did  not  travel  past  the 
shoulders  d  and  e. 

These  conditions  also  prevail  when  the  link-block  is 
placed  coincident  with  the  point  of  suspension  of  the 
link,  at  which  time  the  valve  has  its  least  possible 
amount  of  travel,  the  port  only  opening  to  the  amount 
of  the  lead,  and  the  cut-off  occurring  when  the  piston 


shown  broken  and  shortened,  and  the  valve  spindles 
are  omitted  for  clearness  of  illustration.  The  steam 
ports  are  indicated  by  the  shaded  portions  beneath 
the  valves. 

The  throw  lines  of  the  crank  and  the  eccentric,  are  set 
exactly  in  line  one  with  the  other,  both  being  on  the 
line  of  centers  b  b  of  the  engine,  and  on  the  same  dead 
center. 

The  valve  v  has  opened  the  port  to  the  amount  of  the 


mi-:  roi;  n:n- . \  LL /-;.\   ENGINE. 


151 


lead  as  shown  at  /,  and  it  is  seen  that  from  tlio  position 
of  ana  </,  the  valve  will  be  moved  quickly,  while  arm  I 
will  scarcely  move  the  valve  vf. 

A*  the  mutinii  proceeds  (liie  eccentric,  moving  in  the 
•i-tion  Hi   n>  arrow),  the  it|i|>er  end  of  the   link   will 
move  in  the  direction  of  arrow  x,  and    it,  is  this  tipping 
motion  that  m  u    the    valve    ior    the    admission. 

In  this,  and  in  all  the  (inures,  the  arc  /•  denotes  the  posi 
tion  the  center-line  of  the  link  stands  in  when  the  cra~k 
is  on  its  dead  center,  and  the  parts  in  the  position 
shown  in  Fi^c.  'J.".!i. 

\\"hen  the' parts  have  reached  the  positions  shown  in 


center,  the  link-block  could  he  moved  from  end  to 
end  in  the  link-slot  without  imparting  any  motion  to  the 
valve,  the  lead  uoiiid  lie  eijiwl  for  all  points  of  CUt-off. 

Hut  this  arm  moves  in  an  arc  of  a  circle,  and  the  effect 
of  this  is,  that  if  the  valves  were  set  with  the  crank  on 
the  dead  centers,  the  points  of  cut-off  could  only  be 
e(jual/,ed  for  some  one  point  of  cut-off,  as,  say,  at  half- 
stroke,  lieeaiiM!  when  the  link-block  was  moved  further 
down  the  link,  and  toward  the  line  of  engine  centers, 
the  valve  would  cut  off  earlier  at  the  head  end  than 
at  the  crank  end  of  the  cylinder,  the  difference  being 
considerable  in  the  shorter  points  of  cut-off. 


Mg.  240. 

The  Position  of  the  Parts  when  the  Lead  is  Set  for  the  Head-End  Port. 


Fig.  240,  the  link-block  g  may  be  moved  from  end  to 
end  of  the  link-slot,  without  moving  arm  c  of  the  wrist 
motion  and,  therefore,  without  moving  the  valves,  and 
this  is  the  position  in  which  the  parts  must  stand 
when  the  valve  is  to  be  set  for  this  crank  position. 

If  the  path  of  the  center  (e',  Fig.  239)  of  the  arm  A, 
was  in  a  straight  line  on  the  line  of  engine  centers,  and 
the  link  was  so  set  that,  with  the  crank  on  either  dead 


This,  however,  is  remedied  by  the  construction  shown 
in  Fig.  241,  in  which  the  outer  dotted  circle  represents 
the  path  of  the  crank,  and  the  inner  circle  n  the  path 
of  the  center  of  the  eccentric,  the  line  A  represents  the 
arm  A  in  Figs.  229  and  230,  and  its  upper  extremity, 
e,  represents  the  link-sustaining  pin  whose  arc  of  motion 
is  therefore  arc  a. 

Suppose  we  draw,  below  the  center  C  of  the  crank 


132 


MODERN  STEAM  KXGINES. 


a  vertical  line  A',  equal  in  length  to  the  arm   A,  and 
from  its  lower  extremity,  as  a  center,  draw  an  arc  e" 


\l/ 


r-r    v      /,    Er 
\--t-v       / 


\]> 

V 


Fiij.   241. 
Tinding  the  Positions  of  the  Crank  when  the  Valves  are  Set. 


line  /  /  drawn  to  the  extremities  of  these  two  arcs  will 
be  parallel  to  the  line  of  centers  b  b  of  the  engine. 

From  the  center  C  of  the  crank  shaft,  we  then  draw 
a  line  E,  cutting  the  intersection  of  arc  e"  with  the 
dotted  circle  n,  and  this  line  E  represents  the  position 
the  crank  must  stand  in  when  the  lead  is  set,  and,  at 
this  time,  the  link-block  can  be  moved  from  end  to  end 
of  the  link  without  moving  the  valve.  Similarly,  a  line 
F,  drawn  from  C  and  touching  the  other  end  of  arc  e", 
where  it  cuts  the  circle  n,  gives  the  crank  position  (for 
the  other  piston  stroke)  at  the  time  when  the  link-block 
can  be  moved  from  end  to  end  of  the  link  without 
moving  the  valves,  this  also  being  the  position  the 
crank  is  in  when  the  valves  are  set,  the  lead  for  the 
two  ports  being  made  equal. 

It  follows  from  the  construction  in  Fig.  241,  that 
these  two  crank  positions  are  at  an  equal  distance  below 
the  line  of  centers  b  b,  and  that  the  amount  to  which 
they  are  below  it,  depends  upon  the  proportions  of  the 


Fig.  242. 
Positions  when  the  Head-End  Port  is  Pull  Open. 

passing  through  the  Center  C,  and  this  arc  will  eorres-     various  parts,  which  will   be   treated   upon   hereafter, 
pond  both  in   curvature  and   length  to  the  arc  a,  and  a     Referring;   again  to  Fig.   240,    the  dotted  arc?-  is  the 


Til!-:  PORTER-ALLEN  /-:.Vo7.V/-:. 


153 


position  the  link   \vns   in   when   the  crank   was  on    the 
cl<-;ul  center,  a>  in    Fig-  '-'•'''•'•  '""'  ''"'   amount  of  tipping 

ne  link,  in   tin-  direction  -hown  by   the 

lance  of  arc  /•  from  HIV 

When    tin-    crank    lias    moved     10"     from    tho    dead 
center,    and    the    piston    lias    moved    about  .'rom 

its  dead  center,  the  port  is  full  open   for   the   admission, 
the  •!'   the  parts  being  as  in   Fig.  '_'  12,  in    \vliich 

BIC  /•  represents  the  po.-iiiou  of  the  link,  when  the 
crank  was  on  its  dead  center,  and  shows,  therefore,  the 
amount  the  link  has  moved. 

Referring  now  to  the  amount  of  opening  there  must 


until  the  crank  has  moved  70°  from  the  d, -,-id  center,  at 
which  time  the  parts  occupy  the  positions  shown  in  Fig. 
'.'I  :.  hut  after  tins  the  link  moves  forward  parallel,  the 
port  remaining  full  open  until  the  piston  has  moved 
84°  from  its  dead  center,  the  position  of  the  parts  then 
:  as  in  Fig.  244,  the  opening  at  /,  equalling  one- 
fourth  of  the  ell'ective  area  of  the  port  (or  one-fourth 
the  width  at  ./.  Fig.  235). 

The  piston    has  now  traveled   10  inches   of   its  24 

indies  of  stroke,  and  the  port,  as  the  motion  continues, 

'us  to  close  for  the  cut-off.     The  positions  of  the 

parts,  at  the  time  of  cut-off,  is  sliowu  in  Fig.  245,  the 


•''!/.  243. 


The  Valve  at  the  end  of  its  Travel  for  the  Head-End  Pert. 


be  at  /,  before  the  port  is  open  full  for  the  admission, 
it  is  seen,  in  Fig.  235,  that  the  effective  width  of  the 
port  is  its  width  at  a,  and  as  the  steam  enters  in  the 
four  streams  denoted  by  the  arrows,  it  is  obvious  that 
when  the  opening  denoted  by  the  arrow  b  is  equal  to 
£  the  width  of  a,  the  port  is  virtually  fully  opened. 
As  the  motion  proceeds,  the  link  continues  to  tilt, 


piston  having  moved  1 2  inches,  and  it  is  seen  that  the 
valve  v'  has  scarcely  moved. 

When  the  parts  have  moved  to  the  position  shown  in 
Fig.  246,  the  link  will  again  be  in  such  a  position  that 
the  link-block  <j  may  be  moved  up  and  down  the  link, 
without  imparting  any  motion  to  the  valves.  The  wrist 
arm  d  has  now  moved  to  such  a  position  that  it  imparts 


OFTl! 

I  UNIVERSITY 


154 


MODERN  STEAM  ENGINES. 


Fiys.   244  &  245. 


777 /•;  PORTER-ALLEN  i:\HL\K. 


165 


Fig.  247. 


156 


MODERN  STEAM 


but  little  motion  to  the  valve  >>,  while  wrist  arm  e  is  in 
position  to  move  the  valve  v'  quickly. 


open    to    the    amount  of  its  lead.     The  valve    motion 
has  now  been  investigated  thrughout  one  piston  stroke. 


m 


Fig.   248. 
The  Valve  at  the  End  of  its  Travel  for  the  Crank-End  Fort. 


n 


1 

\ 

—  i 

\ 

y 

/ 

\ 

/ 

i 

\ 

\ 

/ 
i 

\ 

/ 

r 

1 

\ 

/ 

\ 

* 

/2  6 

Fiy.   249. 
Diagram  of  Fort  Openings. 

The  position  of  the  parts,  when  the  crank  arrives  at 
its  dead  center,  is  shown  in  Fig.  247,  the  valve  v'  being 


During  the  next  piston  stroke,  the  motion  varies 
in  two  respects,  first,  the  amount  of  valve  lead  is  great- 
er, for  reasons  which  will  be  explained  presently; 
secondly,  the  port  opens  quicker,  and  remains  fully 
open  longer,  although  the  point  of  cut-off  occurs 
at  the  same  point,  or  at  half -stroke,  as  before. 

Fig.  248  shows  the  position  of  the  parts,  at  the  time 
the  valve  v'  has  traveled  to  the  end  of  its  path  over  the 
port,  and  it  is  seen  that  the  amount  of  opening  at  m,  f  or 
the  admission,  is  greater  than  that  at  /  Fig.  243,  which 
shows  the  corresponding  position  for  the  other  stroke. 
This  occurs  because  the  end  Z  of  the  valve  moves 
further  back  than  does  the  end  c  in  Fig,  243. 

Fig.  249  represents  the  steam  port  openings  during 
the  two  strokes,  the  link-block  being  set  first  to  cut  off 
at  one-half,  and  then  at  one-quarter,  of  the  piston 
stroke,  the  latter  being  marked  in  dotted  lines,  and  it  is 
seen  that,  for  the  cut-off  at  half-stroke,  the  port 


mi-:  i'uim-:i;  ALLEN  KX 


I.-.T 


remains  fully  opened  for  in;  inches  of  one  stroke  (the 
head  end),  and  for  10  inches  on  the.  other,  while  both 
cut-ofTs  occur  at  1.'  inches. 

Similarly,    for    the  cut-off  ;r  Utei  stroke,    tlie 

port  remains  full  o]>en  during  -i1  inches  at  the  crank 
end.  ami  during  ,'!i  inches  at  the  head  end,  the  cut-off 

•  rring  at  the  sixth   inch  on   lioth   strokes.      Fur: 
more,  the  port   is   full   open    when    the  crank   is  on  the 
dead  center  at  the   head  end.  while,  at    the  crank  end,  it 

-  not    open   full   until    the  piston    has    moved  aliotit 
\  inch  for  the  cut-off  at  half  stroke,   and  a!>out  -*  inch 
for  the  cut-off  at  quarter-sir-' • 

Now  the  pi'ston  motion  is.  on  account  of  the  angu- 
larity of  the  connecting  rod.  quickest  when  moving 
fri  111  the  head  end.  and.  therefore,  when  the  port  m  is 
•;g  to  admit  steam.  hence  the  steam  supply  is 
belter  proportioned  to  the  piston  velocity,  than  it  would 
be  if  both  ports  opened  equally. 

It  has  been  observed  that,  in  order  to  equalize  the 
points  of  cut-off  for  all  points  of  cut-off,  it  is  neces- 
sary that  the  arm  A  vibrato  in  an  arc  that  meets 
the  line  of  centers,  when  the  arm  is  vertical  or  at  a 
right  angle  to  the  line  of  centers  b  b  of  the  engine,  and 
that  with  a  proper  adjustment  of  the  parts,  there  are 
two  positions  in  which  the  link-block  can  be  moved 
from  end  to  end  in  the  link-slot,  without  imparting  any 
motion  to  the  valves. 

These  positions  are  those  shown  in  Figs.  240,  and 
LMi',.  the  crank  standing,  in  both  cases,  at  an  equal  dis- 
tance below  the  line  of  centers  k  b,  ready  for  the  valve 
lead  to  be  set.  an  equal  degree  of  lead  being  given  for 
the  two  valves.  When,  however,  the  crank  is  brought 
to  the  respective  dead  centers,  there  will  be  more  lead 
at  the  head  end  than  at  the  crank  end.  as  may  be  seen 
on  comparing  Figs.  239  and  247.  This  is  also  shown 
in  the  diagram  of  the  port  openings  in  Fig.  'J40. 

It  is  obvious,  however,  that  the  lead  might  be  equal- 
ized, if  desired,  by  giving  to  the  valves  an  unequal 
degree  of  lead  when  setting  them  with  the  parts  in  the 
positions  shown  in  Figs.  240  and  24fi,  but  it  is  proper 
to  <rive  an  unequal  lead  when  the  crank  is  on  the  dead 
centers,  and  for  the  following  reasons: 

Let  the  piston  stroke  be  20  inches,  and  the  circle  in 
Fig.  250  being  4  inches  in  diameter,  will  represent  the 
path  of  the  crank-pin  one-fifth  full  size,  and  its  diameter 


on  the  line  from  0,  to  20.  will  represent  the  piston  strcke. 
\Ve  divide  the  circle  into  40  equal  divisions,  represent- 
ing crank  pin  positions,  those  from  1  to  20,  being  for 
the  path  of  the  crank-pin  during  one  piston  stroke,  and 
those  from  '_'((  to  0  representing  crank-pin  positions  for 
the  other  piston  stroke. 

To  find  the  corresponding  piston  positions  we  set  a 
pair  of  compasses  to  represent  the  length  of  the  con- 
nect ing  rod  on  the  same  scale  that  the  circle  represents 
the  path  of  the  crank  pin,  or,  in  this  case,  one-fifth  full 
si/e.  Then  prolong  the  line  0,  20  (which  represents  the 
center  line  of  the  engine),  and  with  the  compasses  set 
as  above,  draw  arcs  from  the  divisions  on  the  circle,  to 
the  line  0,  20,  these  arcs  giving  us,  on  that  line,  the 
ri  position  for  each  crank-pin  position. 

Thus  arc  a  is  drawn  from  division  10,  and  gives  us 
at  I  the  position  of  the  piston  when  the  crank  is  at  point 
or  division  10.  In  the  figure  this  construction  is 
carried  out  from  division  10  to  20,  for  the  last  half  of 
one  stroke,  and  from  division  r,  to  division  0,  for  the 
last  half  of  the  other  piston  stroke. 

We  may  now  compare  the  positions  of  the  piston  on 
one  stroke,  with  its  corresj>onding  position  on  the  other 
as  follows: 

When  the  crank  is  at  division  11,  and  the  piston  at 
c,  the  crank  has  9  divisions  to  move  through  to  com- 
plete the  stroke  (the  crank  being  supposed  to  move  in 
the  direction  of  the  arrow).  The  corresponding  crank- 
pin  position  for  the  next  stroke,  is  at  r,  because  when 
at  r,  it  will  also  have  to  move  through  9  divisions 
before  completing  its  stroke  and  arriving  at  0.  With 
the  crank  at  r,  the  piston  will  be  at  /,  and  we  may  find 
the  difference  between  the  two  piston  positions,  by  draw- 
ingfrom  the  center  C  of  the  outer  circle,  a  semicircle  rf, 
from  which  we  see,  that  with  the  crank  at  the  corres- 
ponding points  1 1  and  r,  of  its  path,  there  is  a  differ- 
ence in  the  piston  positions  represented  by  the  radius 
or  distance  from  e  to  f  (measured  of  course  on  the  line 
0.  20)-  This  difference  is  caused  by  the  angularity  of 
the  connecting-rod,  and  increases  in  proportion,  as  the 
connecting-rod  is  shorter  than  the  crank. 

The  length  of  the  connecting-rod,  in  this  example,  is 
taken  as  three  times  the  length  of  the  piston  stroke,  or 
six  times  the  length  of  the  crank.  By  following  out 
this  method  of  investigation,  we  find  that  while  the  crank 


158 


MODERN  STEAM  ENGINES. 


is  moving  through  the  ten  divisions,  from  10  to  20,  the 
piston  speed  is  less  than  it  is  while  the  crank  is  moving 
through  the  ten  divisions  from  q  to  0,  which  is  clear, 
because,  during  the  one  period,  the  piston  only  moves 


amount  of  linear  motion  at  the  two  ends  of  the  stroke), 
by  means  of  an  unvarying  weight  on  the  crank 
disc,  it  being  obvious  that  the  weight  that  would  coun- 
terbalance the  parts  when  the  piston  is  at  the  crank-eud 


Fig.  250. 


The  Variation  of  the  Piston  Motion. 


from  I  to  20,  while  during  the    other  it  moves  from  b 
toO. 

This  assumes  great  importance  (when  the  piston  has 
a  high  velocity),  because  it  renders  it  impossible  to  coun- 
terbalance the  weight  of  the  piston,  of  the  cross-head, 
and  of  the  connecting-rod  (which  all  have  a  variable 


of    its  stroke,   would  be  insufficient   to  do  so  when  it 
is  at  the  head-end  of  its  stroke. 

It  will  be  noted,  that  as  the  piston  approaches  the 
ends  of  its  stroke,  the  above  variation  diminishes,  and 
that,  so  far  as  the  counterbalancing  is  concerned,  we 
need  only  consider  the  relative  speeds  of  the  piston, 


•/•///•:   PORTER-ALLEN    ENGINE. 


159 


when  reversing  its  motion  at  the  ends  of  the  stroke. 
Suppose,  tlii'ii.  \ve  compare  its  velocity  during  the 
motion  of  the  crank,  while  moving  tin  ia>t 

division  on  each  stroke,  or,  from  19  to  'JO  in  one  case, 
ami  from  /  to  0  in  the  other. 

From  the  piston  position,  when  the  crank  is  at  \'J.  we 
draw  doited  circle  y,  and  we  find  that  it  passes  between 
the  end  (I  and  the  arc  h,  and  the  difference  lietween  the 
distances  of  circle  y  and  arc  h,  from  the  end  0  of  the 
stroke  (measured,  of  course,  on  the  line  0  L'O),  repre- 
sents the  difference  in  the  velocity  with  which  the 

piston  comes  ,to  the  dead  centers,  and  to  its  state  of  rest 
!«•  Tore  beginning  the  next  stroke.  This  difference  is 
about  40  per  cent. 

\Ve  have  :  iimed    the  velocity  of  the  fly-wheel 

and  crank  to  lie  entirelv  uniform,  which,  practically,  it 
is.  Imt  as  the  later  portion  of  the  stroke  is  performed 
under  expansive  steam,  and.  therefore,  tinder  a  reduced 
in  pressure,  it  is  ol.vioiis.  that  the  tendency  is  for 
the  velocity  of  the  lly-wheel  to  reduce  (assuming  the 
engine  load  to  remain  constant),  but  at  whatever 
speed,  or  under  whatever  conditions,  the  engine  may 
run,  the  discrepancy  lietween  the  tly-wheel  and  piston 
velocity  here  descnlicd.  must,  if  the  engine  has  one 
cylinder  only,  exist,  and  the  variation  of  velocity  will  be 
mainly  in  the  piston,  cross-head,  etc.,  and  not  in  the  fly- 
wheel, indeed  it  is  obviously  desirable  to  maintain  the 
velocity  of  the  lly-wheel  as  uniform  as  possible,  so  as  to 
have  a  uniform  velocity  in  the  machinery,  driven  by 
the  engine. 

In  high  speed  engines,  a  uniformity  of  fly-wheel 
velocity  is  more  easily  obtained,  and  maintained,  than 
in  those  running  slower,  for  the  reason  that  the  period 
of  time,  during  which  the  live  steam  is  cut  off  and 
the  fly-wheel  called  upon  to  maintain  the  speed  (not- 
withstanding the  diminished  steam  pressure,  existing 
during  the  expansion  period),  is  diminished. 

It  follows,  from  Fig.  250  and  its  accompanying 
explanation,  that  the  fly-wheel  must,  in  maintaining  a 
uniform  velocity,  maintain  the  inequality  of  piston 
motion,  at  the  two  ends  of  the  stroke,  or,  in  other  words, 
that  this  inequality  is  essential  to  a  uniform  fly-wheel 
velocity,  and  that  the  means  taken  to  counterbalance  the 
piston,  etc.,  must  be  such  as  will  permit  it  to  continue 
until  the  piston  is  near  the  end  of  its  stroke,  when  it 


must  lie  resisted  for  a  length  of  time,  merely  sufficient 
to  avoid  a  kn<>rk  or  //•.»//</  in  reversing  the  motion  of  the 
pi-ton,  etc.,  the  period  varying  with  the  engine  speed. 

It  has  been  already  shown  that  this  cannot  be  done 
for  both  strokes  by  means  of  a  counterbalancing  weight, 
hence,  we  must  resort  to  some  other  means,  which  is 
found  by  giving  the  valve  more'  lead  at  the  head  end, 
than  at  the  crank  end  of  the  stroke,  aa  has  been  des- 
cribed, 

In  proportioning  the  parts  of  an  engine  of  this 
description,  the  distance  from  the  center  of  the  eccen- 
tric to  the  center  of  the  link-slot  is  made  equal  to  six 
times  the  throw  of  the  eccentric,  hence,  since  the  length 
of  the  connecting-rod  is  six  times  the  length  of 
the  crank,  it  bears  the  same  proportion  to  the  throw 
of  the  eccentric  that  the  length  of  the  connecting-rod 
docs  to  that  of  the  crank. 

The  link  supporting  arm  is  also  made  equal  in  length 
to  six  times  the  throw  of  the  eccentric,  and,  with  these 
proportions,  the  cut-off  will  be  at  half-stroke  when  the 
link-block  is  distant  from  the  line  of  centers  to  an 
amount  equal  to  to  six  times  the  throw  of  the  eccentric. 

The  length  of  the  arm  c  of  the  wrist  motion  may  be 
such  that  the  link  will  cause  it  to  make  one-quarter  of 
a  revolution,  so  that  the  arm  d  shall  move  as  much 
past  its  dead  point,  as  it  lacks  of  moving  to  a  position 
at  a  right  angle  to  the  line  of  centers,  or  it  may  be  at 
such  an  angle  to  the  arm  c  that  it  will  move  from  the 
horizontal  to  the  vertical  position,  the  only  appreciable 
effect  being  to  diminish  the  amount  of  retardation  of 
the  valve  movement  while  the  lap  is  traveling  over  the 
port. 

The  wrist  motion  arms  d  and  e,  Figs.  231  and  239, 
may  be  made  as  much  longer  than  c  as  the  width  of 
the  port  may  require,  it  being  obvious  that  by  multiply- 
ing the  motion,  by  making  d  and  e  longer  than  c,  the 
throw  of  the  eccentric  may  be  kept  at  a  minimum. 

The  positions  of  the  eccentric,  and  of  the  link  sup- 
porting arm,  require  to  be  very  exact,  as  the  least  error 
in  their  alignment  one  with  the  other,  or  in  the  height 
of  that  arm,  destroys  the  symmetry  of  the  motion,  and 
also,  the  equalization  of  the  points  of  cut  off. 

Another  point  to  be  considered  in  proportioning  the 
eccentric,  the  link,  and  its  supporting  arm  is,  that 
unless  the  proportions  are  correct  with  relation  one  to 


160 


MODl-:l!.\  .S77-A1J/   /-A 


tlio  other,  the  port  at  the  head-end  will  be  apt  to  have 
no  lead  because  the  lead  is  set  when  the  crank  has 
passed  thf  dead  center.  :ind  moving  it  back  to  that 
renter,  will,  unless  the  above  parts  are  properly  propor- 
tioned, take  oil'  the  lend,  while,  at  the  other  end,  the 
lead  will  be  unduly  increased. 

The  exhaust  valves  being  independent,  the  point  of 
release  and   the  compression  may  be  regulated  at  will. 


TJie   Buckeye   Engine. 

Figures  from    251    to    2GG    represent  the    Buckeye 
high-speed  automatic  cut-oft'  engine. 

Fig.  251  is  a  front  view   of  the   engine,  showing  the 


is  regulated  by  a  governor  attached  to  a  wheel  upon  the 
crank-shaft.  It  differs,  however,  from  other  engines  of 
this  class,  inasmuch  as  that  its  governor  moves  the  cut- 
off eccentric  around  upon  the  shaft,  instead  of  across  it. 
as  is  commonly  the  case,  and  thus  gives  to  both  its 
valves  an  equal  and  constant  amount  of  travel,  which 
pi-events  the  surfaces  from  wearing  unevenly. 

Fig.  253  is  a  horizontal  section  through  the  cylindei 
valves,  steam  chest,  etc.  The  cylinder  section  is  taken 
on  one  continuous  central  plane,  while  the  steam  chest 
and  valves  are  shown  upon  two  planes.  The  first,  and 
nearest  to  the  eye,  extends  from  the  crank  end  of  the 
cylinder  to  the  fracture  at  ///,  and  shows  the  main 
valve  in  section  through  its  center.  From  the  line  of 
fracture  ///,  to  the  head-end  of  the  cylinder,  a  lower 
plane  is  taken,  so  as  to  pass  through  the  center  of 
equilibrium  rings,  or  balance  pistons,  this  lower  plane 


251. 


cross-head,   guide  bars,    and   connecting-rod,  while  thp  |  being  on  the  line  I'  V,  Fig.  254.     This  latter  figure  is  a 


back  view,  Fig.    252,  shows  the    governor   and    valve 
mechanism. 

This  engine  belongs  to  that  class  in   which  the  speed 


sectional  view  on  the  line  A  A,  showing  the  back  of 
the  main  valve  with  the  balancing  pistons  removed 
from  the  crank  end  but  in  place  in  the  head  end. 


Till-:   Bl'i'KKYK    ENGINE. 


161 


Fig.  '_'."i."i  is  a  on  of  die  cylinder  and  valves 

taken  on  tli.>  line  I>  I!  11,  in  Fig.  '2 '>:'>,  so  its  to  pas-; 
through  the  center  of  tin1  vjilvc-i>.-d;mring  pistons  lint 
leave  ihe  end  of  tin-  cut-off  valve  in  full  view. 

Fig.  -.">'!  is  ii  sectional  view  mi  llie  line  ('  <'.'Kig.  -.">.'!. 
anil  shows  the  back  of  the  rut-off  valve  upon  it,s  seat  in 
the  main  valve. 


TIIK  CONSTRUCTION  OF  TIIK   VAI.VKS. 

The  main,  valve  V  is  a  IH.\-  or  elianilier.  fitting  at  each 
end    to  the    cylinder   port     fares,    and   provided     inside 


The  st. -.'mi  from  the  inlet  takes  the  course  shown  in 
Fig.  '->">."..  liy  the  arrows,  tilling  the  chamber  I),  wliirh 
is  ill  one  piece  with  the  valve  rhrstci  >ver.  ahi 

into  the  hark  of  the  valve  through  the  openings  ,/,  ,,f 
which  there  are  four  (two  at  each  end   of  the  •. 
seen   in    Kij;.    '-'">  t.      '1'hr   main    val\e   is   therefore    filled 
with    live    steam,     while    the    exhaust    passes    outside  its 

ends  to  the  outlet.     The  means  employed  to  regulate 
the  pressure  of  the  valve  to  its  seat  are  as  follows: 

The  inner  wall  of  chamber  1)  has,  at  each  end,  a  hub 
I  pored  to  receive  equilibrium  i'in<;.s  or  valve-balancing 
inij  pistons,  these  consisting  of  a  spider  a  (whose  arms 
are  shown  at  a')  the  follower  c,  and  packing  ring  e. 


The  Buckeye  Engine. 


with  a  flat  surface  at  each  end,  whereon  the  cut-off 
valve  v  v'  operates.  The  cylinder  [ports  being  shown  at 
]>'/>".  The  cut-off  valve  consists  of  two  plates  rigidly 
connected  by  means  of  the  stretcher-rods  h  h',  and 
rides  within  the  main  valve,  its  spindle  passing  through 
that  of  the  main  valve. 


The  spider  has  a  guiding  stem  attached  to  its  hub, 
over  which  the  follower  slips  easily.  The  spring  S 
holds  the  follower  and  spider  together,  and  confines  the 
packing  ring  e  in  its  proper  place. 

The  faces  of  the  equilibrium  rings,  or  pistons  a,  gent 
upon  the  back  of  the  main  valve,  and,  therefore,  trans- 


162 


MODERN  STEAM  ENGINES. 


mit  to  the  valve  whatever  steam  pressure  they  receive. 
The  live  steam,  therefore,  holds  the  valve  to  its  seat  by 
acting  on  the  area  enclosed  within  the  circumference  of 
the  four  equilibrium  pistons  a,  and  this  area  is  so  pro- 
portioned as  to  overcome  the  tendency  of  the  valve  to 
lift  from  its  seat.  This  tendency  is  due  to  the  cylin- 
der port  and  the  port  in  the  main  valve,  and  is  greatest 
at  the  moment  of  admission. 

With  the  parts  in  the  position  shown  in  Fig.  253,  for 
example,  it  is  obvious  that  the  steam  in  the  port,  at  the 
head-end  of  the  cylinder,  is  acting  on  the  underneath 
face  of  the  main  valve,  and,  therefore,  in  a  direction  to 
lift  the  valve  from  its  seat,  while,  at  the  same  time,  the 
port  on  that  end  of  the  main  valve  permits  the  steam 
to  press  upon  the  cylinder  face,  and  the  steam  being 
within  the  valve  causes  an  equal  area  on*  the  in 
side  of  the  valve,  and  opposite  to  the  port,  to  be 
unbalanced,  and,  therefore,  act  also  to  lift  the  valve. 

The  area,  however,  of  the  annular  pistons,  is,  as 
before  stated,  proportioned  so  as  to  overcome  these  two 
tendencies  and  hold  the  valve  to  its  seat  sufficiently  to 
keep  its  steam  tight. 

It  is  obvious,  however,  that  when  the  cylinder  port 
is  open  to  the  exhaust,  and  the  cut-off  valve  covers  the 
port  in  the  main  valve,  as  is  the  case  at  the  crank  end 
of  the  cylinder,  in  Fig.  253,  the  pressure  upon  that 
part  of  the  valve  that  covers  the  cylinder  port  is 
reduced  to  that  of  the  exhaust,  while  the  port  in  the 
valve  is  filled  with  steam  that  is  enclosed  between  the 
cylinder  face  and  the  cut-off  valve,  hence,  the  annu- 
lar pistons  would,  in  the  absence  of  any  counteracting 
pressure,  hold  the  valve  more  closely  to  its  seat  than  is 
absolutely  necessary  at  that  end.  But  this  is  provided 
for  by  the  relief  ports  or  recesses,  x  x',  which,  during 
that  portion  of  the  valve  stroke  in  which  it  would  other 
wise  be  held  to  its  seat  with  more  force  than  necessary, 
receive  steam,  through  the  small  hole  shown  to  pass 
through  the  valve  at  r,  and  this  steam,  acting  on  the 
face  of  the  valve,  relieves  it  of  the  undue  pressure 
referred  to.  The  relief  recess  is  equal  in  area  to 
the  cylinder  port,  and  is  so  located  that  it  will  be  uncov- 
ered by  the  heel,  or  inner  edge,  of  the  main  valve  face, 
just  after  the  cylinder  port,  at  -that  end,  is  closed 
against  the  exhaust,  and  before  any  considerable  com- 
pression pressure  can  arise  in  the  cylinder. 


The  steam  hole  r  is  located  to  fill  the  recess  at  the 
proper  time,  which  is  just  after  it  has  been  covered,  as 
above  stated,  by  the  valve  heel. 

It  will  be  seen  'that  the  face  in  of  the  main  valve 
does  not  quite  reach  the  face  of  the  hub  g.  and  that  the 
annular  pistons,  therefore,  project  through  the  bores 
of  g,  and  this  allows  the  main  valve  to  lift  from  the 
seat  to  the  amount  of  the  space  at  m,  in  case  the  cylin- 
der should  receive  a  charge  of  water  with  the  live 
steam.  After  the  water  has  discharged  into  the  exhaust, 
the  steam  pressure  returns  the  valve  to  its  seat,  and  the 
spring  r  causes  the  annular  pistons  to  follow  it  up. 

The  cut-off  valve  is  provided  with  an  inclined  plane 
at  I,  resting  upon  a  corresponding  inclined  plane  pro- 
vided on  the  main  valve,  hence  it  moves  of  its  own 
gravity  up  to  its  seat  on  the  main  valve  and  its  weight 
acts  to  cause  it  to  seat  itself  fairly. 

The  mechanism  for  operating  the  valves  is  as  follows: 

Referring  to  the  general  view,  Fig.  257,  and  the 
cross-sectional  view  of  the  frame  and  rock-shafts  in 
Fig.  258,  the  main  eccentric  is  fixed  upon  the  crank- 
shaft,-and  its  rod  R  drives  the  upper  end  of  the  main 
rocker  (having  journal  bearing  at  ;/,  in  Fig.  258.)  At 
F',  Fig.  258,  it  affords  journal  bearing  for  the  rod  r, 
Fig.  257,  which  drives  the  main  valve  spindle. 

The  cut-off  eccentric  drives  the  rod  S,  which  con- 
nects to  the  lower  arm  s  of  the  cut-off  rocker;  s  is  fast 
upon  A,  which  has  journal  bearing  in  the  main  rocker. 
The  arm  a  is  fast  upon  A,  and  provides  at  E'  journal 
bearing  for  the  rod  that  drives  the  cut-off  valve. 

The  cut-off  eccentric  is  a  working  fit  upon  the  crank- 
shaft, so  that  it  may  be  moved  around  it  by  the  gov- 
ernor, the  construction  being  shown  hereafter  in  con- 
nection with  the  governor.  The  construction  of  the 
valve  rods  is  such  that  the  spindle  for  the  cut-off  valve 
passes  through  that  for  the  main  valve. 

In  Fig.  259,  we  have  the  main  and  cut-off  valves  re- 
moved from  the  other  parts  of  the  engine,  their  spin- 
dles, the  rock-shaft,  the  eccentrics,  and  the  crank  being 
represented  by  their  center-lines. 

For  ease  of  illustration,  the  rods  from  the  rock-shafts 
are  shown  shortened,  and  as  if  connected  direct  to  their 
respective  valves,  which  is  sufficient  for  explaining  the 
action  of  the  mechanism,  while  it  renders  it  easier  to 
illustrate  the  movements  of  the  parts.  The  rods  R  and 


164 


MODERN  STEAM  ENGINES. 


10 
(M 


165 


o 

(M 


U-; 


16(1 


MODERN  STKAM  ENGINES. 


8  correspond  to  R  and  $  in  Fig.  257,  as  is  also  the  case 
with  the  main  and  cut-off  rock-shafts. 

The  crank  is  on   the  (lead  center  B,  and  revolves  in 
the  direction  denoted  bTf  the  arrow.     The  main  eccen- 


upper  arm  a  of  the  cut-off  rock-shaft,  which  is  pivoted 
in  the  main  rock-shaft  at  A. 

Since  both  eccentrics  follow  the  crank  in  the  direction 
of  revolution,   therefore,   when  the  crank  moves  from 


Fig.   251). 
Cross-Section  of  Cylinder  and  Valves. 


trie  is  at  /,  and  the  cut-off  eccentric  at  e.  The  main 
valve  is  operated  by  rod  F,  which  is  driven  by  the 
upper  end  p  of  the  main  rock-shaft.  The  cut-off  valve 
is  operated  by  the  spindle  E,  which  is  driven  by  the 


the  dead  center,  the  valves  move  in  opposite  directions, 
the  main  valve  opening  port  b'  for  the  live  steam.  As 
soon  as  the  cut-off  eccentric  e  passes  the  line  of  centers 
4  J  of  the  engine,  it  operates  the  cut-off  valve  in  the 


TIII-:  BUCKEYE  i-:.\<; ix i-:. 


167 


same  direction  as  tin-  main  valve,  aini  both  valves  move 
in  ttie  same;    direction,     uuiil     such    time  as  the   main 

ntric  y"  has  also  passed  ihc  line  of  centers,  , 
which  the  valves  an-  operated  in  different  directions, 
until  the  cut-oil  vahe  crOBStiC  the  line  of  centers  on  the 
other  dead  center,  at.  which  time,  the  valves  will  again 
7nove  together,  until  tlio  iiiuin  valve  lias  crossed  the 
line  of  centers  at  that  end. 


tions.  But  when  the  cut-oil  eccentric  has  crossed  its 
line  of  centers,  it  moves  rod  S  in  a  direction  opposite 
to  that  in  which  the'  main  rod  R  is  moving,  and  its 
rock  shaft  reverses  tho  direction  of  motion  of  the  valve, 
hence,  both  valves  move  toother  until  the  main  eccen- 
iric.  as  lie  fore  stated,  also  crosses  the  line  of  centers  of 
the  engine. 

The  proportions  of  the  parts,  in  Fig.  261,  are  for  an 


/•'iy.   '-'.">". 


This  occurs  by  reason  of  the  positions  of  the  eccen- 
trics, and  of  the  employment  of  the  cut-off  rock-shaft, 
and  will  bo  readily  perceived,  because,  with  both  eccen- 
trics on  the  same  side  of  the  line  of  centers  of  the 
engine,  they  are  both  moving  in  the  same  direction, 
and,  as  the  cut-off  rock-shaft  s  a,  reverses  the  direction 
of  motion  of  the  cut-off  valve,  while  the  main  valve 
moves  on  the  same  as  if  it  were  connected  direct  to  its 
eccentric,  therefore,  the  valves  move  in  opposite  direc- 


engine  having  a  cylinder  of  14  inches  diameter  and  24 
inches  stroke,  the  throw  of  both  eccentrics  being  1£ 
inches,  giving  to  each  valve  a  travel  of  3  inches.  These 
proportions  give  the  latest  points  of  cut-off  at  five- 
eighths  of  the  stroke,  this  being  the  latest  the  engines 
are  designed  to  have.  Earlier  points  of  cut-off  are 
effected  by  advancing  the  cut-off  eccentric  from  its  posi- 
tion at  e,  in  the  figure,  to  the  position  denoted  by  e'. 
"We  may,  however,  for  the  present,  confine  our  atten- 


OF  THE 

'UNIVERSITY, 


168 


MODERN  STEAM  ENGINES. 


tion  to  the  action  of  the  mechanism,  when  in  position 
for  the  latest  point  of  cut-off,  and,  in  Fig.  262,  we  have 
the  position  of  the  parts  when  the  cut-off  is  effected, 
and  it  is  seen  that  the  main  and  cut-off  valves  are 
moving  in  opposite  directions,  and  that  its  cut-off 
eccentric  is  near  the  point  at  which  it  moves  the  cut-off 
valve  most  rapidly,  hence  it  follows  that  the  cut-off  is 
effected  rapidly.  This  construction  permits  of  the 
employment  of  a  very  short  valve  travel,  thus  reducing 
the  duty  of  operating  the  valves. 

As  the  main  valve  is  driven  bv  an  eccentric  that  is 


Suppose,  now,  that  the  governor  has  moved  the  cut- 
off eccentric  in  position  to  effect  the  cut-off  at  quarter- 
stroke,  and  the  crank  being  on  the  dead  center  B,  the 
positions  of  the  parts  will  be  as  in  Fig.  261,  in  which  it 
is  seen  that  from  the  positions  of  the  eccentrics,  the 
cut-off  valve  will  move  in  the  same  direction,  and  as 
fast  as  the  cut-off  valve. 

The  positions  of  the  parts,  when  the  cut-off  is  effected 
at  quarter-stroke,  is  shown  in  Fig.  262,  and  it  is  seen 
that  from  the  position  of  the  main  eccentric  f,  its  valve 
is  at  rest.  When,  however,  the  cut-off  eccentric  e  has 


Fig.  258. 


Cross-Section  Through  the  Frame  and  Rocker. 


fixed  to  the  crank  shaft,  its  amount  of  travel  is  con- 
stant, and  its  ends  w  in,  pass  over  the  ends  y  and  r  of  its 
seat,  and  as  the  ends  u  w,  of  the  valve,  pass  alternately 
over  the  ends  x  and  n,  of  its  seat,  therefore,  at  all  points 
of  cut-off,  the  tendency  to  wear  the  seat  unevenly 
is  avoided  (this  tendency  existing  when  the  stroke 
of  a  valve  is  decreased). 

In  order  that  the  cut-off  valve  may  similarly  pass 
over  each  end  of  its  seat  on  the  main  valve,  the  shoul- 
ders on  the  faces  d  and  g  are  provided. 


nearly  reached  the  line  of  engine  centers,  the  motion  of 
the  parts  is  such  that  the  two  valves  again  move 
together. 

Fig.  263  shows  the  port  openings  for  the  cut-off  at  f 
stroke,  and  it  is  seen  that,  for  the  head-end  B  of  the 
cylinder,  the  port  is  open  full  at  the  third  inch  of 
piston  motion,  remains  full  open  up  to  the  eighth  inch, 
and  cuts  off  at  the  fifteenth. 

For  the  crank  end,  the  port  is  full  open  at  the  third 
inch,  remains  open  for  8£  inches,  and  cuts  off  at  fifteen. 


UNj 


a 

•8 

3 

1 


•s 

•a 
I 


1B9 


/•///•:  BUCKEYE  I: 


,- 

.V     '171 


The  amount  of  compression  is  I  \  inches  at  each  cud, 
the  ei|iiili/.atioii  being  effected  liy  unequal  laps  at  tin 
two  uiids  (in  «,  Fig.  -.")!•)  ot  (lie  main  valve. 


Hjl 


I 


\ 


\ 


\ 


\ 


\ 


s 


S 


s 


\ 


\ 


\ 


X 


\ 


/Vy.  263. 

t 

Diagram  of  Port  Openings  with  Cut-off  at  Half-stroke. 


The  oxlinust  opening  is.  it  is  scon,  greater  than  the 
steam  port  opening. 

The  lend,  compression,  cushion,  and  exhaust  being 
t_'"\enic,d  l>y  the  main  valve.  having  :t  constant  amount 
of  travel,  obviously  remain  constant  for  all  points  of 
cut-off. 


\ 


\ 


Fig.  264. 

Diagram  of  Port  Openings  with  Cut-off  at  Quarter-stroke. 


The  steam  port  openings,  when  the  cut-off  occurs  at 
quarter-stroke,  is 'shown  in  Fig.  264,  and  the  points  of 
cut-off  are,  it  is  seen,'  equalized. 

22       '-v-;^-.  • 


TIIK 


•"'•"• '    '•'•••   . .-...„ 

'ig.  2(i^  illustraies  1  i,c ..triCchanism  constituting  the 
',  or  speed  rtgjujatbr,  which  advances  the  posi- 
tioii'of.  the  cut  Oil  ecoei'il  ric  upon  die  crank-shaft.  Two 
levers.  /.  (/.lare  pjy.ifted'iit  their  .ends  b  to  arms  of  the 
i;overnor\\,'Jie_e1;,  '  I'poii  these  levers,  and  adjustable 
alon<^  tiSiii'r/ JeiiLTths.  'a re" 'the  respective  weights  A  A. 
en'if.-i'i'  levers' a  (/'connect,  by  ball  and  socketjjoint, 
hi  the  links  B  B;  and'  these  an;  attached,  by  ball  and 
socket  joint,  to  C,  .which  is  in  one  piece  with  the  cut- 
off eccentric,  the  latter  being  a  working  fit  on  the  crank- 
shaft. When  the  wheel  revolves,  tin;  centrifugal  force, 
generated  by  the  weights  A  A  and  the  lever  a  a,  will 
cause  these  parts  to  move  outwards,  as  denoted  by  the 
dotted  lines  in  the  upper  part  of  the  figure.  This  causes 
the  links  B  B  to  advance  the  cut-off  eccentric  upon  the 
shaft  in  the  direction  of  crank-revolution,  thereby  has- 
tening the  point  of  cut-off,  as  has  already  been  ex- 
plained. 

The  outward  motion  of  the  arms  a  a  is  resisted  by 
the  springs  F  F,  and  it  follows  that  when  the  engine  is 
motionless,  or  is  running  too  slow  to  enable  the  centrif- 
ugal force  to  overcome  the  tension  of  the  springs,  these 
springs  will  hold  the  cut-off  eccentric  at  the  position  in 
which  it  effects  the  cut-off  at  the  latest  point  in  the 
stroke,  the  springs  being  under  tension,  and  the  weights 
A  being  held  against  the  wooden  buffers  at/ 

The  further  the  weights  are  situated  from  the  pivoted 
ends  of  the  lever,  the  greater  the  effectiveness  of  the 
centrifugal  force  generated  by  them  at  a  given  speed  of 
governor-revolution,  and  the  further  out  the  levers 
swing,  the  greater  the  amount  of  centrifugal  force  gen- 
erated, because  the  weights  revolve  in  a  larger  circle 
and,  therefore,  at  a  greater  velocity. 

On  the  other  hand,  however,  the  outward  motion  of 
the  levers  and  weights  can  only  occur  by  distending  the 
springs  F  F,  and  the  power  required  to  do  this  increases 
in  proportion  as  the  springs  are  distended. 

the  governor  is  at  rest,  the  force  of  the  springs 
is  static,  but  as  soon  as  the  parts  revolve,  this  force 
becomes  centripetal,  hence,  we  have,  so  far  as  the 


r       ^          ' 

(UNIVERSITY^/ 
V.o> 


172 


MODERN  STEAM  ENGINES. 


weights  and  springs  are  concerned,  two  opposing  forces, 
one  centripetal,  and  the  other  centrifugal,  and  the  most 
perfect  adjustment  of  the  weights  and  spring  tension, 
is  that  in  which,  at  a  given  speed  of  revolution,  these 
two  forces  are  equal  in  amount,  throughout  the  whole 
range  of  movement  of  the  springs  and  levers. 


nal,  or  in  other  words,  it  would  maintain   the  engine 
speed  equal  under  all  changes  of  load. 

In  the  Buckeye  engine,  the  travel  of  the  valve  is  con- 
stant in  amount  for  all  points  of  cut-off,  and  the  power 
required  to  operate  it  is,  therefore,  equal.  But  there  is 
another  element  to  be  considered,  inasmuch  as  that  the 


Fig.  205. 


The  Governor. 


Now,  suppose  the  parts  are  so  accurately  propor- 
tioned, and  the  adjustment  so  correctly  made,  that  this 
equilibrium  of  the  opposing  centrifugal  and  centripetal 
forces  is  established,  and  if  the  power  required  to  oper- 
ate the  valve  is  equal  in  amount  at  all  points  of  cut-off, 
the  action  of  the  governor  would  be  perfectly  isochro- 


weighted  levers  act  (as  they  move  to  different  positions) 
at  a  varying  leverage  to  the  eccentric  wra^  the  following 
result: 

"When  the  weighted  levers  are  in  the  positions  in 
which  they  are  at  the  greatest  leverage  to  the  points  of 
connection  on  the  eccentric,  they  will  obviously  exert 


Till-:  BUCKEYE    ENGINE. 


173 


more  force  in  proportion  to  the  .1!  force  than 

they  would   when  in  thejr  positions  ol    lead   leve 

and  (assuming  the  power  required    to  operate  tin-  valve 
to  be  equal  for  all   points  .  i  the  engine  speed 

will  incr.  in  ord0T   to   maintain    a  ronstanl 

and  equal  speed,  the  centrifugal  force  must,  throughout 


In  the  Buckeye  engine,  the  resistance  offered  by  the 

ion  of  till!   cut-off  eccentric  Hipi    \ai\e   gear   is  een- 

:al  in  its  tendency.     This   tendency  i*  »f  greatest 

effect  when  the  levers    a  a  are   at  their  extremes  of 

movement,  and  the  auxiliary  springs  P  P,  Fig.  266,  are 

employed  to  correct  it. 


C" 
I' 

e" 


/•'/,/.   266. 


Diagram  of  Speed  Regulation. 


the  whole  range  of  lever  movement,  bear  a  constant 
and  equal  proportion  to  the  total  force  resisting  it,  this 
total  force  including  the  power  required  to  operate  the 
valve  as  well  as  that  required  to  resist  the  tension  of 
the  springs. 


Those  auxiliary  springs  are  intended  to  start  the 
levers  out  at  the  proper  speed  when  the  tension  given  to 
the  main  springs  is  that  proper  to  secure  the  best  regula- 
tion during  the  outer  half  of  their  range  of  movement, 
where  it  is  mainly  confined  when. the  engine  is  properly 


174 


MODKHX  ,STf,Vl.lf  ENGINES. 


loaded.  Under  such  an  adjustment  of  tension,  it  was 
found  that  the  centripetal  tendency  of  the  resistance 
offered  by  the  cut-off  valve  and  gear,  being  augmented 
in  effect  in  an  increasing  ratio  from  mid-movement  in- 
wards, in  proportion  to  the  increasing  acuteness  of  the 
angle  formed  by  the  links  with  the  eccentric  ears,  re. 
quired  more  than  the  mean  working  speed  to  overcome 
it,  and  the  auxiliary  springs  are  made  of  such  force  as 
to  just  overcome  this  undue  frictioiial  centripetal  ten- 
dency. They  leave  contact  at  mid-movement,  where 
they  are  no  longer  needed,  the  above  tendency  being 
then  at  its  minimum.  Its  increase  from  mid-movement 
outwards  is  provided  for  in  the  tension  of  the  main 
springs,  which  is  increased  on  that  account  to  obtain  a 
diminished  ratio  of  increase  of  spring  force. 

The  range  of  lever  motion  is  sufficient  to  regulate  the 
speed  under  all  changes  of  load  under  all  ordinary  con- 
ditions of  boiler  pressure,  and  it  is  obvious  that  the 
ratio  of  the  centripetal  to  the  centrifugal  force  will 
remain  the  same  whatever  changes  may  occur  in  either 
the  engine  load  or  the  boiler  pressure. 


DIAGRAM    GRAPHICALLY  ILLUSTRATING  SPEED    REGULA- 
TION AND  THE    USE  OF    THE    AUXILIARY  SPRINGS. 


To  graphically  illustrate  the  variation  of  the  effective 
centripetal  and  centrifugal  forces,  and  the  use  of  the 
auxiliary  springs,  let  the  line  a  A,  in  Fig.  266,  represent 
the  length  of  the  piston  stroke  divided  by  lines  repre- 
senting points  of  cut-off  at  |.  £,  §,  £  and  £  stroke.  The 
vertical  line  a  P  is  equally  divided  into  lines  represent- 
ing speeds. 

Now,  suppose  that  while  the  levers  move  from  the 
inner  to  the  outer  end  of  the  range  of  motion,  the 
distance  of  the  center  of  centrifugal  force,  from  the 
center  of  the  shaft,  is  doubled,  and  the  amount  of  cen- 
trifugal force  will  be  doubled.  And  if  the  total  spring 
tension,  resisting  the  centrifugal  force,  is  also  doubled 
at  tho  same  time,  the  two  forces  will  increase  in  the 


same  ratio,  and  the  speed  regulation  will  be  isochronal. 
Such  regulation  may  lie  represented,  so  far  as  the 
centrifugal  force  is  concerned,  by  a  line  I  I'  parallel  to 
a  A. 

Now,  suppose  that  tho  centripetal  friction  would 
accelerate  the  speed  at  the  earliest  cut-off  by  an  amount 
represented  by  the  distance  from  b  to  c ;  at  ^  cut-off 
by  the  distance  <•',  and  at  f  cut-off  by  the  distance  c" 
from  line  I  b',  and  through  these  points  we  may  draw 
a  curved  line  repi-esenting,  in  its  curvature  upwards, 
the  amount  to  which  the  centripetal  friction  would 
accelerate  the  speed;  this  acceleration  being  represented, 
ai  |  cut-off,  by  the  distance  V  c';  at  the  earliest  cut-off 
by  the  amount  b  c;  and  at  $•  cut-off  by  the  distance 
//  ,•". 

This  shows  close  regulation  at  and  near  c',  but  near 
'•  there  will  be  a  change  of  speed  accompanying  changes 
of  cut-off,  and  to  remedy  this,  more  spring  tension  is 
required. 

From  c'  to  c",  the  speed  variation  is  shown,  by  the 
upward  curvature  of  the  line,  to  be  in  the  wrong  direc- 
tion, lierause,  while  the  point  of  cut-off  would  be  pass- 
ing from  c'  towards  c",  the  speed  would  be  accelera- 
ting, whereas,  the  engine  load  is  increasing,  and  its  ten- 
dency is.  therefore,  to  decrease  the  speed,  hence,  for 
this  part,  the  tension  is  too  great,  because,  with  less 
tension,  the  diminution  of  spring  force  would  be  more 
rapid,  which  would  compensate  for  the  increasing  effect- 
iveness of  the  centripetal  friction. 

I'.y  the  application  of  the  auxiliary  springs  P  P,  Fig. 
265,  the  speed  may  be  cut  down  from  c"  to//.  This 
will  give  stability  of  speed  throughout  all  points  of 
cut-off  from  ^,  or  c',  to  £,  or  //,  leaving  a  margin  of 
variation  for  points  of  cut-off  between  ^  and  /cro,  which 
margin  is  represented  by  radius  d  c. 

This  margin  may,  however,  be  diminished,  to  any 
required  extent,  by  giving  a  spring  tension  that 
would  give  the  fastest  speeds  at  the  latest  cut-offs,  as 
represented  by  the  line  d  d',  and  on  this  line  we  may 
draw  the  assumed  frictional  curve,  e  e'  e",  correspond- 
ing to  line  c  c'  c",  and  it  is  seen  that  from  e  to  e',  it  is 
sufficiently  isochronal,  and  by  changing  e'  e"  to  e'  d', 
by  means  of  the  auxiliary  springs,  the  regulation  be- 
comes sufficiently  isochronal  throughout  the  whole  range 
of  cut-off. 


€SE 
VERS 
OF 
V-li-C'. 


Tin-:  .1  I:MISI;T<>\-  SIMS  /•: \  i ;  / \ /•:. 


175 


TJie 


l'ji<jin<>. 


In  l-'iirs.  L'I;;  and    '_'i;s.  we    ha\e  t\vu  viewi  of   tin- 
Armington-SiniB  hi^h   -peed   Automatic  mi-oil  en{ 

the  ci,ii>tnirlion  Keinj;  us  follows: 

F;g.  269  ia  a  vertical  section  of  the  cylinder  and  valve. 

tin-    latter    lieinu    a    jiistcui    viilvc   iiinl  iloi. 

ill    Kiir. _'.'7ii,    in   wliicli   it  is   sliown    lirokt-n.     'I'lif 
port  a  i<  r.H-. -i\  iiiLr  ,t,.;nn  tlinni>j;!i  iiln-rs.  ili>noti'il 


•_r  through  this 
throiiL'li  tin'  ralve,  and  liml-  /;    into  the  annu- 

lar L:  ...  into  port,  'i.     'I'd,.  ojxMiing,  de- 

ooted  by  arrows  <  v,  I'xti-inls  all  iinmii'l  the  circumfer- 
•  •nr,.  of  ihc  v.-ilvi-.  and  the  sti-nin  passes  directly  into 
tin'  annular  groove  and  pur; 

cxliaii.-t    p  at  the  end  of   tlie  valve,  as 

|jy  tlic  arrow  al    I!,  and  is.  tlii'ri'l'ore,  independ- 
ent  of   the  admission. 

The  lap  of  i  he  valve  is  marked  in   Fig.  271,  in  which 
it  is  .  ihe  valve  just,  close-   the  porl  a,  and  will 

keep  it  dosed  for  the  jM-riml  of  expansion,  or  until  the 
valve  has  moved  far  enough  to  the  ri^ht  to  open  the 


Fiy.   267. 


The  Armington-Sim*  Engine. 


by  the  four  arrows,  the  valve  being  hollow,  and  it  is 
olivious,  that  the  opening  denoted  l,\-  arrows  <•  <l,  ex- 
tends around  the  whole  circumference,  with  th<;  excep- 
tion of  the  metal  at  e,  of  which  there  are  four  sections 
in  the  circumference  of  the  valve. 


exhaust,  as  in  Fig.  272,  this  poriod  of  motion  corres- 
ponding to  the  passage  of  the  steam  lap  of  a  simple 
slide  valve  over  the  port. 

The  compression  begins  when  the  end  m  of  ihe  valve 
covers  the  port,  as  in  Fig.  '2~'l,  and  increases  in  amount 


176 


MODi-:uy  ST/-:AM  ENGINES. 


as  the  valve  travel  is  reduced  and  the  cut-off  occurs 
earlier,  as  will  be  seen  hereafter. 

The  engine  speed  is  governed,  and  the  point  of  cut-off 
varied  to  suit  the  load,  by  a  mechanism  that  varies 
the  travel  of  the  valve,  but  maintains  the  lead  equal  at 
whatever  point  in  the  stroke  the  cut-off  may  occur,  tin- 
construction  being  as  follows:  Figs.  273  and  '-'74, 
show  the  construction  of  the  regulator  or  governor,  re- 
moved from  the  main  shaft. 

The  weights  1  1  are  pivoted  at  their  outer  ends  to  the 


In  moving  the  inner  eccentric  C  forward,  its  angular 
advance,  and,  therefore,  the  amount  of  valve  lead  is 
obviously  increased,  and  in  moving  the  eccentric  ring  D 
l>ack\vard.  the  eccentricity  of  the  combined  eccentrics 
(C  and  D)  is  reduced,  and  thus  reduces  the  valve  travel. 

The  necessity  for  increasing  the  lead,  in  proportion  as 
the  amount  of  valve  travel  is  reduced,  is  shown  in  Fig. 
'JT.'i.  in  which  A  represents  the  common  throw  line  of 
the  two  eccentrics,  the  rod  being  at  e,  and  it  is  seen, 
that  if  we  move  the  point  of  connection  e  of  the  rod 


Fig.  268, 

The  Armingtoa-Sims  Engine. 


arms  of  the  wheel,  and  to  these  weights  are  pivoted  the 
links  2  2,  which  at  their  other  ends  are  pivoted  to  the 
inner  eccentric,  which  is  a  working  fit  on  the  cran-k- 
shaft.  To  one  of  these  weights  the  lever  3  is  pivoted, 
its  other  end  being  pivoted  to  the  outer  eccentric  or 
eccentric  ring,  as  it  may  be  termed,  hence,  as  the  wheel 
revolves,  the  centrifugal  force  of  the  weights  causes 
them  to  move  outwards  at  their  free  ends,  thus  turning 
the  two  eccentrics  npon  the  shaft,  and  thereby  altering 
both  their  total  amount  of  throw,  and  the  position  of 
the  common  throw  line  with  relation  to  the  crank. 


along  the  line  A  and  towards  C,  we  shall  move  the  valve 
to  the  right  and  decrease  the  opening  or  lead  at  c; 
hence,  to  maintain  a  constant  degree  of  valve  lead,  we 
must  increase  the  angular  advance  of  the  eccentric,  it 
being  borne  in  mind  that  the  eccentric  and  eccentric 
ring  are.  in  effect,  a  simple  eccentric,  capable  of  adjust- 
ing the  amount  of  valve  travel  and  of  maintaining  the 
lead  constant,  and  it  may  be  remarked  that  the  throw 
line  of  the  two,  or,  in  other  words,  their  line  of  great- 
est eccentricity,  always  passes  from  the  center  of  the 
shaft  through  the  center  of  the  eccentric  ring. 


Till:  ARMING  TON-SIMS,  ENGINE. 


177 


In  Fig.   276,  for  example,   the  en-rut  nVs 
with   their   throw    line    A    at    65°    l'r<>ni     tlie    ennik.    the 


E  l*ing  at  e,  and   that  of  the 
riii-:   !!  >  ;hat  the  throw  line  A  passes 


Fig. 


Fig.  27-J. 


Fig.  271. 


The  Valve. 


/'y.  269. 
Section  through  the  Cylinder  and  Valve. 


178 


MODERN  STEAM  ENGINES. 


from  C  through  /     The  dotted  circle  a  is  drawn  from     the   crank,  and    it  is   seen   that   the   throw-line  A   still 


the  crank  center  C,  and  shows  that  the  line  A  A,  is  the 


passes   from  C    through    the   center  /  of  the  eccentric 


Fig.   273. 


l-'i'j.    274. 


The  Governor. 


Fig.  275. 


common  throw-line  of  the  two  eccentrics  (E  and  R), 
and  also  that  the  amount  of  travel  the  valve  would 
have  is  the  radius  G.  In  Fig.  '-'77.  the  eccentric  E  has 
been  moved  forward,  and  the  ring  R  moved  back,  caus- 
ing their  common  throw-line  A  to  stand  44°  behind 


ring  R,  the  amount  of  valve  travel  being  reduced  to 
the  radius  G'. 

To  find  the  position  of  the  common  throw-line  A,  for 
the  two  eccentrics  for  any  required  poiut  of  cut-off,  we 
proceed  as  follows: 


Till-:  ARM1SGTON-SIMS   K \ < ; I \ /•:. 


179 


In   Fig.   '_>7S.   lot  tho  outor,  or  largo  circle,    represent 
the  path  of  tin'  crank-pin  center,  and  required 

to  find  the  position   for  tho  (-(11111111)11  throw-line  of  tho 


further  to  tho  left  hand  in  ordor  to  open  port  a  full  for 
tho  admission  «f  Meain,  and  to  whatever  amoupt  it 
loaves  t lie  edge  A  of  port  a,  it  must  move  back  the 


Fig.  277. 


Fig.  278. 


Finding  the  Position  of  the  Eccentric. 


two  eccentrics,  the  cut-off  to  occur  when  the  piston  has 
moved  seven-tenths  of  its  stroke,  and  the  crank  stands 
at  K,  its  direction  of  motion  being  denoted  by  the 
arrow.  On  the  right  of  the  figure,  we  have  the  valve 
in  the  position  it  would  occupy  when  the  crank  was  on 
the  dead  center  B,  and  it  is  clear  that  the  port  o,  being 
open  to  the  amount  of  lead  only,  the  valve  must  move 


same  distance  before  it  can  close  the  port  and  effect  the 
cut-off.  Now,  when  the  valve  is  at  the  end  of  its 
stroke,  the  common  throw-line  A,  of  the  two  eccentrics, 
must  be  on  the  line  B  C,  and  it  is  clear  that,  suppos- 
ing the  valve  to  have  no  lead,  three  things  must  happen. 
First  (omitting  all  considerations  as  to  the  crank 
position),  the  common  throw-line  A  will  move  towards 


180 


MODERN  STEAM  ENGINES. 


b  during  the  whole  time  the  port  a  is  being  opened. 
Second,  this  throw-line  will  stand  at  b  when  the  port 
a  is  full  open,  the  valve  being  at  the  end  of  its  travel. 
and  third,  the  throw-line  A  will  move  past  R,  while 
closing  the  port  a,  to  the  same  distance  it  did  in  open- 
ing it.. 

The  amount  of  this  distance  (measured  on  the  crank 
circle  BID,  and  supposing  the  valve  to  have  1:0  lead) 
will  obviously  be  half  the  distance  between  K  and  1>. 
which  we  obtain  by  arcs  s  drawn  from  K  and  B  respect- 
ively. With  the  compasses  set  to  the  radius  B  s, 
we  mark,  from  B,  the  arc  at  g,  and  it  is  clear  that  if  the 
crank  is  at  B  and  the  throw-line  at  g  C,  then,  while  the 
crank  moves  from  B  to  s,  the  common  throw-line  A 
will  move  from  g  to  B,  and  the  port  will  be  opening. 
Then,  while  the  crank  is  moving  from  s  to  K,  the  com- 
mon throw-line  will  move  from  B  to  s,  and  the  cut-off 
will  occur.  It  has  been  supposed  that  the  valve  had  no 
lead,  but  we  may  now  take  the  lead  into  account  as 
follows: 

As  the  inner  circle  represents  the  path  of  the  com- 
mon center  of  the  two  eccentrics,  therefore  its  diameter 


Fig.  279. 

J  n,  represents  the  travel  of  the  valve.  Now,  it  has 
been  shown  that  with  no  valve  lead,  the  common  throw- 
line  of  the  eccentrics  would  stand  at  ij  when  the  crank 
was  at  B.  From  g  we  draw  a  line  to  C,  and  where  this 
cuts  the  inner  circle,  we  erect  a  vertical  line  d. 

From  d  mark  off  the  amount  of  valve  lead,  and  draw 
the  line  /  parallel  to  line  d;  from  C  draw  a  line  e  e, 
cutting  the  line  f  at  its  junction  with  the  inner  circle, 
this  line  e  giving  the  position  for  the  eccentric  when  the 


crank  is  at  B.  By  prolonging  this  line  to  e',  and  mark- 
ing, from  e'  to  P,  a  distance  on  the  outer  circle  equal  to 
the  distance  from  B  to  K,  we  get  the  angle  the  common 
throw-line  moves  through  while  the  crank  moves  from 
B  to  K,  taking  the  lead  into  account 

In  Fig.  279.  we  have  a  similar  example,  the  cut-off 
to  occur  when  the  crank  arrives  at  K.  By  dividing 
the  arc  B  K,  we  get  arc  B  s,  and  mark  B  <j  equal  to  B  .<., 
we  then  draw  <j  C,  this  being  the  position  of  the  com- 
mon throw-line  when  the  crank  is  at  B  and  the  eccentric 
has  no  lead.  From  g  C  we  mark  d,  and  distant  from  d 
to  the  amount  of  valve  lead,  we  mark  f,  and  a  line  e, 
from  G  to  the  intersection  of  /  with  the  inner  circle 
(which  represents  the  path  of  the  common  center  of 
the  two  eccentrics),  is  the  common  throw-line  corres- 
ponding to  lines  A  in  Figs.  276  and  277. 

Instead  of  using  two  circles,  one  for  the  crank-pin 
path  and  one  for  the  path  of  the  common  center  of  the 
two  eccentrics,  however,  we  may  use  a  single  circle  to 


find  the  angle  of  the  common  throw-line  necessary  to 
cut-off  at  any  given  point  in  the  piston  stroke. 

Let  it  be  required,  for  example,  to  find  the  angle  of 
the  common  throw-line  to  the  crank  necessary  to  effect 
the  cut-off  when  the  piston  is  at  half-stroke,  and  we 
draw  the  circle,  in  Fig.  280,  representing  the  path  of 
the  crank  on  one  scale,  and  the  path  of  the  common 


Tin-:  .\i;.Mi\<;'r»s  SIMS  ENGINE. 


1S1 


center  of  tin-  t\vi>  eccentrics  on  another  scale,  or  it  may 
i'lll  si/e  if  tin-  amount  of  valve  travel  has  liecii  de 
tenniiie.l.  Suppose  the  crank  to  lie  at  1!  ail' I  the  cut -oil 
is  to  occur  when  the  crank  is  at  K.  the  piston  then 
being  at  half-stroke,  ami  we  take  half  the  an;  I!  K.  ami 
from  I!  mark  oil  pointy.  I  'ig  the  posit  ion  of 

common   throw-line   when    the    valve   has    no   lead. 
from  ./  we  erect  the    vertical  line    ,/.  ami  to   the  left   0 
ami  distant  from  it  to  the  amount  of  the  lead,  we  draw 
A   and  where  /  cuts   the   circle,  as   at  e,  we   draw  a  line 

which  gives  the  angle  of  the  common  throw-line  of 
the  two  ecce*ntr:c<  to  ih.-  crank  necessary  to  enable  the 
cut-oil  to  occur  when  the  crank  readies  K. 


TIIK    V.VI.VK    PROPORTIONS. 

The  amount    the    valve   leaves  the   port   open   is  obvi- 
ously equal   i.  .nice    from  <l  to   U  measured  on 


valve   travel   necessary    for   the   point  of  cut-off  corros. 
ponding  to  the  angle  of  eccentric. 

The  point  of  cut  off  having,  however,  been  deter- 
mined, and  the  angle  of  the  eccentric  to  the  crank 
found  by  the,  foregoing  construction,  we  may  propor- 
the  amount  of  travel  to  suit  the  width  of  the  port. 
Suppo-e.  for  example,  that  the  steam  port  in  the  cylin- 
der requires  to  have  an  opening  of  an  inch  and  we  may 
proportion  the  valve  as  in  Fig.  '2S1,  the  width  at  -  heinic 
only  sufficient  to  give  the  necessary  s!rem_rth,  because  it 
has  no  elTect  upon  the  distribution  of  the  steam,  where 
as,  the  wider  it  is  the  wider  the  port  must  be,  and  thi 
increases  the  clearance  space. 

The  width  of  the  port  d  must  be  not  less  than  the 
sum  obtained  by  subtracting  the  width  of  the  metal,  at 
c,  from  the  width  of  the  port  and  dividing  the  remain- 
der by  '2,  so  that,  when  the  valve  is  in  the  position 
shown  in  the  figure,  c  being  in  the  middle  of  the  width 
of  port  a,  the  opening  will  ue  equal  on  each  side  of  c, 
and  the  port  being  fully  opened,  there  will  be  an  open- 


Fig.  281. 


the  lino  C  B,  but,  as  the  valve  takes  steam  at  both  ends, 
the  amount  of  effective  opening  is  twice  d  B.  It  will 
now  be  seen  that  there  is,  for  each  point  of  cut-off,  a 
definite  decree  of  angle  of  eccentric  to  the  crank,  and 
that  this  angle  cannot  be  departed  from,  except  in  so 
far  as  concerns  the  amount  of  lead  given,  and  it  follows 
that  the  motion  of  the  eccentric  and  the  ring,  when 
moved  by  the  weighted  levers  1  1,  in  Fig.  273,  must  be 
such  as  to  cause  the  common  throw-line  A,  Fig.  277. 
to  stand  at  the  proper  angle  to  the  crank,  and  at  the 
same  time  regulate  the  degree  of  eccentricity  of  the 
center  f  in  that  figure  so  as  to  give  the  amount  of 


ing  at  the  end  denoted  by  the  arrows  /,  equal  to  one 
half  the  effective  width  of  the  port  a.  It  is  obvious 
that  if  the  width  of  ports  d  was  less  than  this,  the  ad- 
mission would  be  correspondingly  diminished,  but  that 
it  may  be  made  greater  without  affecting  or  increasing 
the  effective  amount  of  port  opening. 

The  dimension  y  may  be  proportioned  so  as  to  either 
equalize  the  point  of  release  for  the  two  strokes,  or  so 
aslo  equalize  the  point  at  which  the  compression  will  be 
effected. 

Tho  diameter  of  the  valve  may  be  made  such  thru 
its  circumference  equals  the  diameter  of  the  cylinder 


1S2  MODERN  STEAM  ESGINES. 

tlici  length  of  the  port  equaling   the   piston    diameter.  |  recess  r,  thus  closing  the  port  d  and  leaving  r  full  open, 


7 


N 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


\ 


Fig.  2S2. 
Port  Openings  for  Cut-Off  at  Half-Stroke. 


\ 


/$ 


\ 


\ 


\ 


\ 


h^ 


\ 


\ 


\ 


/ 


Fig.  283. 
Port  Openings  for  Cut-Off  at  Seven-tenths  Stroke. 


The  valve  travel,  for  the  latest  point  of  cut-off,  is  such 
as  will,  at  the  end  of  the  valve  travel,  bring  the  inner 
edge  of  the  port  d  coincident  with  the  edge  s  of  the 


save  where  it  is  covered  \>j  the  thickness  of  the  metal 


at  c. 


Now,  suppose  the  effective  width  of  port  opening  is 


THI-:  M;MI.\<;TU.\  SIMS  ENGINE. 


183 


required  to  Vie   an  inch,  and  the  width  of  the  annular 

;:il  tin-  thickness  lit  i1  plus   I    inch. 

i-iit-ulT  is  to  In-  at  seven- 

tenths  <if  the   piston  stroke,  and    we  iu;iy   lind  the  ri« 
sarv    po-iiions   of  the   eccentrics,    as:   in     Fig.    2~i!.    the 
c'lMitniiii  tli row  line   being   found    to   lie  ;,.'i    liehin.l  tlie 
crank. 

If  the  thickness  a;  then  tW  an   elTective  port 

ojM'iiinur  of  mi  ineli.  the  annular  recess  must  be  If  indies 
and  the  port  •/  4   inch   wide,  so  that    when   the  vnl  . 
in    the   position    it    occupies   in    Fig.  -sl.   there    will    lie 
4  inch  openrng  at/  and  \  inch  at  •/.  and  as  tin-  motion 
.•initiiines  in   Hie   direction  of  the  arrow   I,,  the  opening 


/r 


\ 


\ 


\ 


s 


X 


s 


s 


\ 


\ 


\ 


N 


\ 


Fig.  '-'si 


Fort  Openings  at  Quarter  Cut-off. 


denoted  by  the  arrow  e,  will  increase  as  rapidly  as  port 
d  closes.  The  travel  of  the  valve  must,  therefore,  be 
equal  to  the  effective  width  of  the  port  (in  this  case  1 
inch)  plus  the  length  of  g,  which  may,  as  before  re- 
marked, be  proportioned  to  equalize  the  points  of  re- 
lease or  of  compression.  Suppose  the  points  of  release 
are  to  occur  at  the  23rd  inch  of  piston  motion,  the 
total  piston  stroke  being  24  inches,  and  the  length  of  ij 
must  be  1  j  inches  at  the  head  end.  and  1}|  inches  at 
the  crank  end,  and  the  travel  of  the  valve  being  4 
inches,  the  port  openings  will  be  as  in  Fig.  282,  where 
it  is  seen  that,  at  the  crank  end  B,  the  port  is  open  full 


when  the  piston  has  moved  about  |  inch,  remains 
open  full  for  r.'j  inches,  while  the  cut-off  occurs  at 
lOj  inches  and  ;•  at  23  inches. 

For  the  poii  at,  the  head  end,  the  admisrton  is  full 
when  the  piston  has  moved  half  an  inch,  remains  full 
open  up  to  the  l.")th  inch,  the  cut-off  occurs  at  the  18th 
inch  and  the  release  at  the  23rd  inch.  The  amount  of 
cushion  is  :;j  for  one  stroke,  and  about  4J  for  the  other. 

In  order  to  ell'.  it-off  at  half-stroke,  the  gov- 

ernor must  have  moved  the  eccentrics  to  the  position 
shown  in  Fig.  'J77.  the  common  throw-line  A  standing 
at  I  I  liehind  the  crank,  and,  in  order  to  maintain  the 
lead  ccjual  the  valve  travel  must  lie  reduced  from  4  to 
::  inches.  The  disposition  of  the  steam  is  as  shown  in 
Fig.  2s:i.  the  port  at  the  crank  end  B  being  fully 
ojKMied  at  the  2nd  inch  of  piston  motion,  remaining 
full  open  for  6  inches,  cutting  off  at  12  inches. 

The  exhaust  begins  at  2 If  inches,  and  the  compres- 
sion, on  the  return  stroke,  at  1 8£  inches. 

When  the  piston  moves  from  the  crank-end  D,  the 
point  of  cut-off  is  at  13^  inches,  the  release  at  22},  and 
compression  begins  at  17i  inches.  It  is  seen  that  in  pro- 
portion as  the  point  of  cut-off  is  earlier  in  the  stroke, 
the  release  occurs  earlier,  and  the  amount  of  com- 
pression is  increased. 

It  will  be  observed  that  the  exhaust  does  not  fully 
open,  but  it  is  to  be  borne  in  mind  that  the  port,  when 
acting  as  an  exhaust  port,  has  a  greater  effective  width 
than  it  has  as  a  steam  port,  being,  in  this  example,  1 
inch  wide  .as  a  steam  port,  and  1  f  wide  as  an  exhaust 
port.  This  occurs  from  the  fact  that  the  thickness  of 
the  metal  on  the  valve  at  c,  Fig.  281,  must  be  de- 
ducted from  the  width  of  the  port,  when  considering  it 
as  a  steam  port,  but  not  when  considering  it  as  an  ex- 
haust port. 

For  the  cut-off  at  ^  stroke,  the  common  throw-line  of 
the  eccentrics  must  stand  at  23°  behind  the  crank,  and 
the  travel  will  be  reduced  to  2i  inches,  the  steam  dis- 
tribution being  as  shown  in  the  diagram,  Fig.  2S4.  It 
is  seen  here  that  the  port  does  not  open  full  for  either 
the  admission  or  the  exhaust,  while  the  compression 
(which  is  shown  for  one  stroke  only,  viz.,  the  crank-end 
port)  occurs  at  14£  inches,  giving  5£  inches  of  compres- 
sion. The  exhaust  is  here  again  earlier,  occurring  at 
the  19th  inch  in  the  stroke. 


€~ff£. 
or  THE 
VER 
*f' 


ITY) 


18-1 


MODERN  STI-:AM  ENGINES. 


ONIVEF 


Till:  STRAIGHT-LINE  ENGINE. 


i  as 


Tin'  XI ra i "lit  Line   r. 


In   i  -    f n mi   •_'*;>   to     ."(!•_',    is     illustrated   the 

Line  engine.   designed  .lolni    K. 

.-?  \vcet  i't'    S\  racii-e  .\.-\v  N". 

name  Straighl    !  LVen  UM-HUSC  the.    (illtlilics 


rvs  c,f  niai-lsi-.l    iiulividiiality.  <lcsiiirin-'i  to  inert   the 

if  the  hi^h   jiistnu  stieol    that  ha- 

a  marked    Icature   of  modern    [''•  lhat 

steam  ti.Lclit.  arc  madn  SO  by  accurately 
lilted  jiarts.  ami  arc  kcj.t  so  liy  siiiijile  means  of  correct- 
inir.  or  lakinj;  up.  the  wear,  i  g  willi  the  jiackint; 

commonly  used,  and,  therefore,  reducing  to  a  mini- 
muni,  the  cost  of  maintaining  tlu^  ciiirine  in  good  work- 
ing order  and  of  running  it. 

The  motions  of  the  working  parts  are  all  direct  and 


Fig.   287. 
Horizontal  Section  through  the  Cylinder  and  Valve. 


of  the  engine  are  in  the  direction  of  the  strains,  and 
are  therefore,  straight   lines- 

Throughout  the  details  of  this  engine  will  be  found 


are  positive,  while  by  an  original,  ingenious,  and  simple 
arrangement  of  parts,  an  automatic  cut-off  is  obtained 
from  a  single  eccentric  and  valve,  the  latter  giving 


186 


MODERN  STEAM  ENGINES. 


practically  equalized  points  of  cut-oil,  while  the  lead  is 
varied  equally  for  the  two  ports. 

Fig.  285  is  a  side  elevation,  and  Fig.  28<;  a  plan  of 
the  engine,  and  it  will  be  seen  that  the  frame  runs 
direct  from  the  cylinder  to  the  main-shaft  bearings. 

The  fly-wheels  run  between  two  bearings,  and  one  of 
them  contains  the  governor  or  speed  regulator.  The 
frame  rests  upon  three  legs  or  points,  thus  ensuring 
that  it  shall  bed  fairly  upon  its  foundations,  whether 
the  same  be  unstable  or  not.  The  two  side  membei-s  of 
the  frame  are  connected  by  a  cross  rib,  on  which  are 
the  bearings  for  the  rock-shaft,  while  the  guide-Liars  are 
contained  within  a  rigid  portion  of  the  frame. 

Referring  now  to  the  details   of   construction,    Fig. 


Fig.  288. 
Vertical  Section  through  Cylinder. 

287  represents  a  horizontal  section  through  the  cylinder 
and  Fig.  288  a  vertical  section  through  the  same,  while 
Fig.  289  is  a  side,  and  end  view  of  the  piston  removed 
from  the  cylinder. 

The  piston  is  hollow,  and  therefore  light  in  propor- 
tion to  its  length,  it  is  secured  to  its  rod  by  two  taper 
seats  and  a  parallel  thread,  which  is  made  an  easy  fit,  so 
as  to  prevent  its  influencing  the  fit  of  the  taper  seats. 

The  piston  packing  is  constructed  as  follows:  The 
rings  are  made  in  two  sections,  the  lower  of  which  is 
driven  tightly  in  the  grooves  and  faced  off  even  with 
the  piston  surface.  The  joint  openings  are  made  very 


narrow,  and  as  the  joint  faces  are  horizontal,  (as  seen  in 
the  end  view,  Fig.  289),  therefore  these  openings  do 
not  increase  as  the  rings  open  out  to  compensate  for  the 
wear. 

Moreover,  the  openings,  being  near  the  bottom  of 
the  piston  which  rests  on  the  bore  of  the  cylinder,  are 
virtually  closed  by  the  piston.  The  upper  parts  of  the 
rings  are  made  £  inch  larger  in  diameter  than  the  cvl- 


Side  Elevation. 


Sectional  End  Vim-. 
Fig.   2 SI). 

The  Piston. 

inder,  and  are  closed  and  sprung  into  their  places,  being 
what  are  termed  snap  rings,  and  it  follows,  that  being 
in  two  parts,  the  ring  will  conform  itself  much  more 
readily  and  correctly  to  the  cylinder  bore,  than  is  the 
case  when  the  ring  has  a  single  split. 

In  place  of  the  ordinary  gland  and  its  accompanying 
packing,  a  single  Babbit-metal  bushing  is  employed  as 
shown,  being  a  free  sliding  fit  which  is  found  to  be 
sufficient  to  prevent  leakage  of  steam,  because  of  the 


Till:  X7YM  IUJJT  LIXE  EXniXE. 


187 


24 


The  (Jovernor. 


Fig.  290. 


183 


MODERN  KTEAM  ENGINES. 


brief  period  the  piston  occupies  in  making  a  stroke 
being  too  short  to  permit  the  steam  to  pass  through. 
The  bushing  rests  in  a  spherical  seat,  being  mamtaiin'il 
therein  by  the  steam  pressure  as  well  as  by  an  outside 
collar. 

The  bushing  is,  therefore,  free  to  move  laterally  with 
the  piston  rod,  and  this  leaves  the  duty  of  guiding  the 
piston-rod  entirely  upon  the  piston  and  guide  bars, 
where  it  properly  belongs,  and  thus  prevents  the  bore 
of  the  bushing  from  wearing  by  reason  of  the  piston- 
rod  moving  laterally  as  the  guide-bars,  etc.,  become 
worn. 

The  valve  and  its  operating  mechanism  is  constructed 
as  follows:  Fig.  '.'90  represents  the  governor,  rock-shaft 
and  valve  removed  from  the  engine.  The  eccentric  is 
suspended  from  a  lever  that  is  pivoted  to  the  face  of 
the  wheel  at  a,  and  is  connected,  at  its  end  A,  to 
arms  or  links  B  and  C.  Link  C  is  connected  to  a  spring 
D,  which,  when  the  engine  is  in  motion,  exerts  a  ten- 
sion acting  to  move  the  eccentric  across  its  shaft, 
and,  therefore,  to  increase  the  valve  travel,  so  as  to 
prolong  the  point  of  cut-off. 

Link  B  is  pivoted  to  a  lever  E,  which,  in  turn,  is 
pivoted  to  an  arm  of  the  wheel,  and  weighted  at  its 
other  end.  "When  the  wheel  revolves,  the  centrifugal 
force  generated  by  the  heavy  end  of  the  lever  E,  acts 
in  a  direction  to  move  that  end  outwards,  and,  there- 
fore, to  move  the  eccentric  inwards  across  the  shaft,  re- 
ducing its  throw,  and,  therefore,  the  valve  travel,  thus 
hastening  the  point  of  cut-off. 

These  opposing  forces  are  so  regulated,  in  the  strength 
of  the  spring  and  the  weight  of  the  heavy  end  of  the 
lever  E,  that  up  to  the  time  the  engine  has  attained  its 
proper  speed,  the  eccentric  is  at  its  greatest  throw  and 
the  cut-off  is  at  its  latest  point  in  the  piston  stroke,  but 
if  the  conditions  (such  as  a  sudden  decrease  in  the 
engine  load  or  duty)  are  such  as  tend  to  induce  an  in- 
crease of  speed,  the  increased  centrifugal  force,  gener- 
ated by  the  heavy  end  of  E,  moves  the  eccentric  inward 
across  the  shaft,  and  thereby  hastens  the  point  of  cut- 
off. In  the  contingency  of  the  spring  breaking,  there- 
fore, the  eccentric  would  be  moved  by  lever  E  to  its 
point  of  least  throw  or  central  upon  the  shaft,  and  the 
engine  would  stop. 

Now,  suppose  the  engine  to  be  running  at  its  normal 


speed  under  a  heavy  load,  and,  as  the  eccentric  will  be 
at  its  greatest  throw,  therefore  its  center  will  be  at  its 
greatest  distance  from  the  axis  of  its  shaft,  hence  the 
centrifugal  force,  generated  by  the  eccentric  itself,  will 
be  in  a  direction  to  cause  it  to  move  still  further  out- 
wards, and  in  opposition  to  the  heavy  end  of  lever  E, 
and  as  the  lever  A  is  pivoted  at  one  end  only,  while  the 
other  swings  outward  with  the  eccentric,  it  also  will 
generate  a  centrifugal  force  opposing  that  generated  by 
the  heavy  end  of  E.  But  on  the  other  hand,  however, 
the  spring  D,  being  fast  at  one  end  only,  its  free  end 
generates  a  centrifugal  force  acting  in  the  same  direc- 
tion as  the  lever  E,  and,  therefore,  to  counteract  the 
unbalanced  centrifugal  force  of  the  eccentric  and  lever  A. 

Furthermore,  as  the  conditions  lead  towards  an  in- 
crease of  speed,  the  eccentric  is  moved  more  central  to 
its  shaft  (carrying  with  it  the  lever  A),  hence  it  revolves 
in  a  path  of  less  diameter  and  generates  less  unbal- 
anced centrifugal  force,  and,  as  a  result,  there  is  less  re- 
sistance to  the  prompt  action  of  the  governor  in  the 
necessary  direction.  The  friction  of  the  eccentric  in 
its  strap  has  no  influence  upon  the  spring  or  lever  E, 
and  does  not,  therefore,  disturb  the  eccentric  moving 
mechanism. 

The  equilibrium  thus  obtained,  is  sufficient  to  practi- 
cally relieve  the  spring  and  lever  E  from  the  disturbing 
elements,  sometimes  found,  of  a  varying  unbalanced  cen- 
trifugal force  generated  by  the  governor  mechanism 
when  moved  to  different  positions  to  answer  the  re- 
quirement of  varying  the  point  of  cut-off. 

Another  characteristic  of  the  governor,  is  that  the 
weight  of  the  governor  ball  (as  the  weight  on  the  lever 
E  is  termed)  is  such  as  to  practically  counterbalance 
the  weight  of  the  eccentric  and  its  strap.  The  object 
of  this  is  to  prevent  the  weight  of  the  eccentric  and  its 
strap  from  disturbing  the  proper  circular  path  through 
which  the  eccentric  center  should  rotate,  and  thus  obvi- 
ate the  disturbance  that  would  occur  from  the  tendency 
of  the  eccentric  and  strap  to  fall  towards  the  shaft  when 
above  it,  and  fall  away  from  the  shaft  when  below  it,  in 
the  path  of  revolution,  this  tendency  existing  unless 
counteracted  by  this,  or  by  some  other  means. 

The  joints  of  the  levers  B  and  C  Fig.  290,  of  the 
governor  are  (to  reduce  friction  and  obviate  the  neces- 
sity of  oiling  them)  constructed  as  in  Fig.  291,  the  eye 


Till-:  STi;. I  Kill  T-/JM-:  ENGINE.  is:, 

having  a  flat  plate  of  tempered   steel   upon    which  the     constant  contact  with  that  side  only,  of  the  eye,  on  which 


Fig.  292. 


F<<j.  291. 

the  steel  plate  is  placed.  The  pivot  joint  of  lever  E, 
Kig-  -'.HI,  has  a  large  nil  hole  drilled  through  the  center 
of  its  pin,  ami  from  this  hole  smaller  holes  are  pierced 
to  the  wearing  surface  of  the  pin.  The  central  hoie  is 
plugged  at  its  outer  end,  and  thus  forms  an  oil  pocket 
or  reservoir  affording  continuous  lubrication. 

Fig.  292  is  a  sectional  view  through  the  rocker-shaft, 
and  shows  the  means  of  maintaining  the  valve-rod  in 
line.  The  lower  rocker-arm  carries  a  pin  having  jour- 
nal bearing  in  a  block,  sliding  vertically  in  a  box  into 
which  the  end  of  the  valve-rod  is  secured.  This  box 


"3 


Fig.  293. 


The  Valve  Construction. 


pins    roll,   this   construction    being  available    because, 
from  the  tension  of  the  spring  D,  the  pins  are  held  in 


slides  along  a  guide,  and  is  kept  down  to  its  seat  on  the 
guide  by  means  of  a  segment  that  is  shown  attached  to 


190 


MODERN  STEAM  ENGINES. 


the  rocker  hub,  and  seated  on  top  of  the  ]>ox.  The 
block  obviously  moves  in  the  arc  described  by  the  ]>in 
in  the  rocker-arm,  and,  therefore,  moves  vertically  in 


Fig.   294. 


the  box  which  is  covered  by  a  gib  on  which  die  seg- 
ment rolls  as  the  rocker  swings,  hence,  the  segment  not 
only  keeps  the  box  to  its  seat  on  the  guide  beneath  it, 
'but  also  acts  to  relieve  the  rocker  bearings  of  the 
weight  of  the  rocker-shaft. 

The  construction  of  the  valve,  and  the  means  of 
eliminating  the  pressure  to  its  seat  that  exists  in  an 
ordinary  slide-valve,  is  shown  in  figure  2911,  in  which 
on  the  left,  is  shown  a  sectional  view  of  one  end  of  the 
cylinder,  and  on  the  right,  a  side  view  of  the  valve 


Fig.  295. 

removed  from  the  steam  chest,  (a  top  view  of  the  valve. 
in  section,  is  shown  in  Fig.  287).  The  valve  is,  it  will 
be  seen,  a  rectangular  frame  having  four  ports  p.  the 
ribs  between  the  ports  being  kept  rigid  by  the  pieces  e, 
which  are  solid  with  the  valve,  but  do  not  extend  to  its 
face. 

A  rectangular  piece  n,  rests  on  the  lower  face  C  of 
the  valve  chest,  and  on  this  rests  the  valve  v.  On  the 
top  of  the  valve  is  a  rectangular  piece,  or  bar  m.  cor- 


responding to  piece  n,  and  at  the  back  of   the  valve  is 
a  shield,  or  pressure  relieving  piece  P.     The  pieces  m 


Fig.   296. 


Fig.   297. 


Fig.  298. 


Fig.    2'.lO. 

Valve  Positions. 

and  11,  therefore,  form   distance   pieces,  leaving  between 
the  face  of  P  and  the  face,  or  valve  seat  R,   an  opening 


TIIK  STRAIGHT-LINE  ENGINE. 


191 


in  which  the  valve  may  slide  I'r.  .  rare, 

Mi-k.       \Vhen.    in    I;  •  \  alve 

ttud,  i:  may  be  surfaced  true,  and  the 

lucci]  in  restore  the  lii  ol  the  valve  in 

opening    in    which 

refining    is  greatly  facilitated,  because  ;ili  may 

I  e  • .  '••.•Under,  ami  surfaced    cither  in   a 

chine,  or  i  •  nch.  insi.  "inuring  to  U- 

:"am  chot  \vlicrc  it  is  difficult    to 

To  fully  uiide  action  of  the  valve,  ami  tin- 

to 

con.-ider  n    when    in     position    for    th. 

uts  (luring  the 

In    \'"\£.    '.".it    i;;.'   crank-em!    |>ort  a,    and    a 
the  valve  aip!  plate    1'.  Is    shown,  ami    il   i-    seen 

tha:  ive  port  opening  is  ilon'nlc  the   amount   to 

which    the   valve   has    •  the    port  the 

live-  .steam     is    admitted     to    port   n   in    two    place-. 
ficiioteil  i,y  ihe  arro\vs  .    am]  /. 

ung    remains  at   iloulili-   that 
due   to    thai    :iino:  •!!.    until     I 

own  in  Fig.  I'!!.".,  after  which,  the 

amount    •  -ening   remains  a     constant     <|uanlity 

unli  -  readied  tlie    position   shown    in    Ki^. 

•-".til.  after  which,  the  opening  remains  the  same  as  for 
a  common  slide  valve,  tin-  maxiinuni  of  valve  travel 
being  ahowa  in  Fig.  '.'iiy.  When  the  poin:  off  is 

at  half  stroke,  ihe  valve  opens  the  port  for  admission  to 
the  anio  Pig.  -jur,.  il1(,  opening  at  /  and  at 

ji  ln-ing    equal. 

1'   :-  it  by  means  of  port  /*,  the  port 

ning  is.   for  all  points  of  cnt-ofF  up    to  half-stroke. 

doubled  throughout  tin.-  whole  of  tho  admission  period, 

ami  that  for  points  of  cut-off  later  than   half-stroke,    it 

is  doubled  up  to   half  piston  stroke,    remains  stationary 

for  a  certain    period   depending  on   the  point  of  cut-oil. 

and  for  still  later  points,  continues  the  port  opening  the 

ic  us  a  common  slide  valve. 

The  action   is  similar  when  the  valve  moves  on    its 

return  stroke  to  effect  the  cut-off,  the  amount  of  port 

uing  heinjr  doubled  from  the  position  shown  in   Fig. 

•J!»i!  until  final  cut-off,  which  prevents  wire  drawing  the 

un. 

We  have  now  to  consider  the  exhaust,  and  by  means 


of  the  port // iii  t  i  .  this  also  is  double  that  due 

to  the  motion  of  the  valve,  as  may  be  seen  in  Fig.  'Jits, 
in  which  the  valve  is  shown  in  the  position  it  occupies 
when  the  exhaust  begins,  the  steam  having  two  means 
.it  U  denote,!  by  the  arrows.  The  double  port 
opening  continues  during  the  same  part  of  the  piston 
'notion,  i  a  port  opening  does  for  the  admission. 

'"'cause  the  ]•         '          the  same    effect    upon  the  ex- 
haust, as  port  /i  has  for  the  admission. 

Tin-  shield  G,  in  the  figures,  is  provided  because  it, 
was  found  that  in  their  absence,  the  exhaust  steam 
flowing  in  the  direction  denoted  by  the  arrow  in  Fig. 
•J'.Mi.  would,  in  time,  cutaway  the  face  of  the  pressure 
relieving  plain  P,  at  n. 


THK   KITKXTHIC',    HOCKKIi,    AND  VAI.VK  MOVKMKNTS. 


\\'e  have  now  to  consider  the  means  by  which  the 
points  of  cut-off  for  the  two  .strokes  are  maintained 
practically  eqimlixcd  for  all  points  of  cut-off,  and  the 
lead  varied  equally  for  the  two  strokes.  In  Fig.  300 
let  "\V  represent  tin-  rim  of  the  governor  wheel,  and 
suppose  the  crank  to  be  at  D  and  the  eccentric  (at  its 
greatest  throw)  at  e.  Let  the  eccentric  center  when 
moved  across  the  shaft  to  its  position  of  least  throw,  lie 
at/  and  it  is  obvious,  that  the  path  of  the  eccentric 
in  moving  across  the  shaft,  would  be  along  the  line  e  / 
At  a  right  angle  to  this  line,  and  from  the  center  C  of 
its  length,  we  draw  a  line  C  C'.  and  then  with  the  length 
of  the  eccentric-rod  as  a  radius,  and  from  C  as  a  center, 
we  mark  an  arc  d,  giving  at  g  the  position  for  the  eccen- 
tric-rod eye  corresponding  to  crank  position  D.  The 
length  of  the  eccentric-rod  (measured  from  the  center 
of  the  eccentric),  is  radius  g  e,  and  it  is  clear,  that  if. 
the  eccentric-rod  being  pivoted  at  y,  we  move  its  other 
end  across  the  shaft,  it  will  move  in  a  line  that  will, 
(from  the  great  length  of  the  rod),  practically  coincide 
with  the  line  e  /. 

\Ve  may  now  turn  to  the  lever  (A  Fig.  L'90).  that 
moves  the  eccentric  across  the  shaft,  and  as  its  fixed 
end  is  pivoted  at  h  on  the  line  C  C",  it  is  olivious,  that 


192 


MODERN  STEAM   KXCINES. 


if  \ve  move  its  other  end  across  the  shaft,  the  eccentric 
center  will  move  in  an  arc,  that  from  the  length  h  c 
and  for  the  short  distance  e  f,  practically  coincides  with 
line  e  f. 

Now  suppose  the  crank  to  move  to  its  dead  center  B, 
and  the  center  of  the  eccentric,  when  at  its  greatest 
throw,  will  have  moved  to  e',  or,  if  at  its  least  throw, 
will  have  moved  from  /  to  /',  we  therefore  draw  a  line 
from  /  to  f,  and  at  a  right  angle  to  this  line,  and  from 


the  middle  of  its  length,  we  draw  a  line 


Then, 


with  the  length  of  the  eccentric-rod  as  a  radius,  we 
mark  an  arc  n,  giving  us  at  p  the  position  of  the  eccen. 
trie-rod  eye  corresponding  to  crank  position  B,  and  it 
is  clear  that  if  we  swing  the  eccentric-rod  on  its  pivot 
P,  its  other  end  will  move  in  a  line  that  will  practically 
coincide  with  line  e  f,  because  of  the  great  length  of 
the  rod  and  the  short  distance  from  t'  to  /'. 

"While  the  crank  moves  from  B  to  D,  the  lever  (A 
Fig.  290)  that  moves  the  eccentric  across  the  shaft,  will 
move  from  position  h  to  position  /;',  which  is  in  line 
with  line  in  in',  and  in  a  position,  therefore,  to  move  the 
eccentric  in  a  path  that  will  practically  coincide  with 
line  e'  /'. 


THE   POSITION     OF     THE    ROCK-SHAFT. 

"We  have  now  to  find  the  position  for  the  center  of 
the  rock-shaft,  which  may  be  done  by  taking  the 
length  of  the  upper  arm  of  the  rock-shaft  as  a  radius, 
and  from  g  as  a  center,  marking  an  arc  s  s.  With  the 
same  radius,  and  from  p  as  a  center,  an  arc  r  r  is 
marked,  the  point  of  intersection  of  arcs  r  and  s  being 
the  location  for  the  center  of  the  rock-shaft. 

The  position  of  the  lower  arm  of  the  rock-shaft, 
or,  in  other  words,  its  angle  to  the  upper  arm,  may  be 
found  as  follows: 

The  crank  being  at  D,  and  supposing  the  valve  to 
have  no  lead,  it  will  be  in  the  position  shown  at  G,  (the 
eccentric-rod  eye  being  at  g)  and  will  be  moved  from  its 
mid-position  to  the  amount  of  the  steam  lap,  the  lower 
arm  of  the  rock-shaft,  will,  therefore,  have  moved 
from  its  mid-position  to  the  same  amount,  hence,  we 
mark  an  arc  u  and  arc  v,  distant  from  the  line  t  to  the 


amount  of  the  steam  lap,  and  draw  the  lower  rocker-arm, 
cutting  the  arc  a  where  arc  v  cuts  it. 

As  the  valve  is  double  ported,  ample  admission  is 
obtained  with  a  minimum  of  valve  travel,  and  as  the 
upper  arm  of  the  rocker  is  longer  than  the  lower  arm 
of  the  same,  therefore  the  action  of  the  eccentric  is 
reduced,  or,  in  other  words,  the  path  of  the  eccentric 
center,  is  of  larger  diameter  than  would  be  the  case  if 
both  rocker-arms  were  of  equal  lengths.  By  this 
menus,  the  duty  of  the  governor  in  shifting  the  eccen- 
tric is  lightened,  thus  enabling  the  employment  of  a 
minimum  of  weight  on  the  end  of  lever  A. 


THE  EQUALIZATION  OF  THE  PISTOX  AND  VALVE  MOVEMENT. 


Having  found  the  positions  of  the  various  parts,  we 
may  now  trace  their  movements  as  follows: 

Suppose  that  the  crank  is  at  D,  Fig.  301,  and  the 
eccentric  center  at  e,  and  the  eccentric-rod  eye  will  be 
at  g  and  the  valve  in  the  position  shown  at  G.  Now 
while  the  eccentric  center  moves  from  e  to  11,  the  rod  end 
will  move  to  position  q  and  the  valve  to  position  N,  the 
port  b  being  opened  to  its  fullest  extent;  and  while  the 
eccentric  center  moves  from  n  to  w,  the  valve  will  move 
back,  and  when  at  w,  will  close  the  port  ft  and  effect  the 
cut-off,  having  returned  to  the  position  it  occupies  at  G 
in  the  figure. 

While  the  eccentric  moves  from  w  to  e',  the  valve 
will  move  from  its  position  at  G  to  its  position  at  H, 
ready  for  port  a  to  open,  the  piston  having  completed 
its  stroke  while  the  crank  and  eccentric  center  have 
made  a  half-revolution. 

A  pair  of  compasses  are  then  set  to  the  length  e  g 
of  the  eccentric-rod,  and  resting  one  point  at  n,  we 
mark  an  arc,  giving  us  at  q  the  position  of  the  ecccen- 
tric-rod  on  the  arc  a;  cc  of  motion,  of  the  upper  end  of 
the  rock -shaft. 

Similarly,  to  find  the  position  of  the  eccentric-rod  eye 
when  the  eccentric  center  is  at  w,  we  rest  the  compasses 
at  w  and  mark  an  arc,  giving  us  at  g  the  position  of  the 
eccentric-rod  eye. 

Turning  now  to  the  piston  stroke,  while  the  crank 
moves  from  B  to  D,  with  the  crank  at  B  and  the  eccen 


THE 


J-:M:L\K. 


193 


I 

I 

I 


194 


MODERN  STEAM  EXGINKS. 


trie  at  e',  the  eccentric-rod  eye  is  at  p.  While  the 
eccentric  center  moves  from  e'  to  n',  the  rod  eye  moves 
from  ji  to  s,  fully  opening  the  steam  port  a  in  the 
figures,  and  while  the  eccentric  center  moves  from  n'  to 
k,  the  rod  moves  from  s  back  to  p,  closing  port  a  for 
the  cut-off,  the  valve  occupying  the  position  shown  at 
H.  Finally,  while  the  eccentric  center  moves  from  k 
to  e,  the  rod  moves  from  ji  to  </,  and  the  valve  from  the 
position  shown  at  H  to  that  shown  at  G,  thus  completing 
a  full  revolution. 

Now  suppose  we  take  the  path  of  the  crank-pin,  and 
divide  its  circumference  into  24  equal  divisions,  a.-.  •<' 
b'  c'  d'  etc.,  and  let  the  diameter  of  the  circle  on  the 
line  D  B  represent  the  path  of  the  piston.  Then,  if  we 
take  the  length  of  the  connecting-rod,  measured  on  the 
same  scale  as  the  circle  represents  the  path  of  the  crank- 
pin,  we  may  rest  one  compass-point  on  the  line  of 
centers  (or  line  D  B  continued  from  D  past  B),  and 
from  the  divisions,  mark  the  corresponding  piston  posi- 
tions. Thus,  suppose  the  crank  has  moved  from  D  to  r't 
and  the  piston  will  have  moved  from  D  to  arc  1  at  the 
crank  end;  when  the  crank  .has  reached  division  s'  on 
the  circle,  the  piston  will  have  reached  arc  2  on  the  line 
D  B,  and  so  on  throughout  the  whole  revolution. 

When  the  crank  has  moved  from  D  to  y,  it  will  have 
made  a  quarter-revolution,  but  the  piston  will  not  have 
moved  half  its  stroke,  as  it  should  do  to  keep  time  with 
the  crank  motion.  On  the  other  hand,  however,  while 
the  crank  moves  the  quarter-revolution  from  y  to  B,  the 
piston  will  move  from  arc  6  to  B,  which  is  more  than 
half  its  stroke.  Similarly,  while  the  crank  moves  the 
quarter-revolution  from  B  through  divisions  a'  V  c'  etc., 
to  y',  the  piston  will  move  through  the  divisions  from  1 
to  6  at  the  head  end,  and,  therefore,  more  than 
half  its  stroke,  and  it  is  shown,  that  the  piston  moves 
faster  when  moving  from  the  head  end  B  to  arc  6,  than 
it  does  when  moving  from  the  crank-end  D  to  arc  6, 
and  it  is  this  that  causes  the  points  of  cut-off  to  vary  in 
engines  having  a  common  or  simple  slide-valve  with 
equal  lap  for  each  port. 

Now  the  nature  of  the  eccentric  motion  in  the 
Straight-Line  Engine,  is,  in  connection  with  the  line  of 
motion  of  the  eccentric-rod  and  rocker-shaft,  such  as 
to  correct  this  evil  without  the  employment  of  unequal 
lap  on  the  valve,  while  at  the  same  time,  it  main- 


tains the  lead  equal  at  each  end  of  the  cylinder. 
Tims,  on  the  piston-stroke  when  the  crank  is  moving 
from  D  towards  B,  it  has  been  shown  that  the  port  will 
be  fully  opened  when  the  eccentric  center  is  at  n,  and 
that  the  cut-off  occurs  when  the  eccentric  reaches  w, 
hence,  the  angle  the  eccentric  moves  through  while  it 
is  closing  the  valve,  is  angle  n  w,  or,  in  this  exam- 
ple, 63°  as  marked  in  the  figure.  On  the  other  stroke, 
when  the  motion  of  both  piston  and  crank  (on  their 
respective  paths)  is  from  B  to  D,  the  eccentric,  in 
operating  the  valve  to  close  the  port  and  effect  the  cut- 
off, moves  (as  has  been  shown)  from  n  to  k,  which  is  in 
this  example  58°,  as  marked,  it  is  clear  then,  that  since 
the  speed  of  the  crank  is  uniform,  the  cut-off  will  be 
effected  quicker  when  the  crank  is  moving  from  1!  to  D, 
than  it  will  be  when  the  crank  is  moving  from  D  to  B. 
We  have,  therefore,  that  when  the  piston  is  performing 
the  stroke  from  B  to  D.  during  which  it  is  moving  at 
its  quickest  when  compared  with  the  crank  motion,  the 
action  of  the  eccentric  and  valve  motion,  is,  from  its 
peculiar  construction,  also  accelerated,  so  that  the  valve 
action  is  timed  with  the  piston  motion.  Similarly, 
when  the  piston  is  moving  through  its  stroke  from  D  to 
B,  during  which  its  speed  is  the  slowest  when  compared 
with  the  crank  motion,  the  mechanism  delays  the  valve 
speed  and  again  times  the  valve  action  with  the  piston 
speed,  and  it  is  apparent  that  a  length  of  connecting-rod 
may  be  chosen,  that  will  give  a  piston  motion  that  will 
have  exactly  equalized  points  of  cut-off  for  the  two 
piston  strokes,  let  the  eccentric  be  moved  to  any  position 
across  the  shaft  that  it  may.  This  will  be  seen  because, 
to  whatever  position  across  the  shaft  the  eccentric  may 
be  moved,  the  periods  of  valve  closure  for  the  cut-off 
will  be  within  the  angle  n  w  for  one  stroke,  and  n'  k  for 
the  other;  the  latter  will  always  be  less  than  the  former, 
and  always  less  to  the  same  amount,  while  the  piston 
speed  will  also  vary  to  the  same  amount  for  the  two 
strokes. 

Another  feature  of  this  valve  motion  is  that  it  gives 
a  much  larger  port  opening  at  the  head  end  of  the 
cylinder  than  at  the  crank  end,  and  thus  gives  a  greater 
admission  for  the  stroke,  when  the  piston  is  moving  the 
fastest.  Thus,  when  the  eccentric  is  at  e  the  upper  end 
of  the  rocker  is  at  g,  when  the  eccentric  is  at  n  the 
rocker  is  at  q,  giving  a  full  port  opening  at  that  end  of 


/•///•:  STRAIGHT-LINE  l-:\<iL\K. 


195 


S 

QJ 

ca 


g 


105 


MODERN  STEAM  ENGINES. 


the  cylinder.     Similarly,  when  the  eccentric  is  at  e',  the 
rocker    is  at  p,  and    when  the  eccentric  is  at    n',  the 


302 


rocker  is  at  s.  Now,  as  the  distance  from  p  to  s  is 
greater  than  from  p  to  q,  therefore  the  port  opening 
for  the  end  of  the  cylinder  furthest  from  the  crank,  is 
larger  than  the  port  opening  at  the  crank  end  of  the 
cylinder,  which  is  necessary,  not  only  on  account  of  the 
quicker  piston  motion,  but  also  because,  at  the  crank- 
end.  the  piston-rod  reduces  the  steam  space  by  an 


amount  ranging  between  from  2  to  7  per  cent,  hence, 
the  head-end  port  requires  a  corresponding  increase  of 
opening  to  keep  the  steam  pressure  up  to  the  same  point 
as  that  obtained  in  the  crank-end  of  the  cylinder. 

Fig.  302  shows  the  details  of  construction  of  the 
cross-head,  which  is  made  hollow  and  as  light  as  is 
consistent  with  the  requisite  strength.  The  cross-head 
pin  is  held  secure  in  the  connecting-rod  end,  and  has 
journal-bearing  in  the  cross-head,  by  this  means,  a  long 
journal-bearing  is  secured  and  the  connecting-rod  is 
prevented  from  moving  sideways  at  its  crank-end.  The 
surface  of  the  cross-head  pin  is  cut  away  at  the  top  and 
bottom,  and  the  corresponding  surface  in  the  cross-head 
bore  is  recessed,  which  prevents  the  pin  from  wearing 
oval.  The  recess  is  so  arranged  that  the  bearing  surface 
on  the  pin  passes  over  the  edges  of  the  recess,  thus 
preventing  the  formation  of  shoulders. 


Tlie  Ide  Engine- 

Figures  from  303  to  316  illustrate  a  High  Speed 
Automatic  Cut-off  Engine,  designed  and  constructed  by 
A.  L.  Ide  and  Son. 

Figure  303  is  a  side  elevation  of  the  engine,  and 
figures  304  and  305  elevations  on  a  larger  scale,  and 
partly  in  section  to  show  the  construction  and  the  valve 
mechanism. 

The  piston  is  hollow,  and  is  provided  with  two  snap 
piston  rings.  The  piston  valve  operates  in  steel  bush- 
ings, that  may  readily  be  removed  when  worn,  the 
valve  and  bushings  being  shown  removed  from  the 
engine  in  Fig.  306.  The  bushings  are  each  provided 
with  openings  through  which  the  steam  passes  into  the 
cylinder  when  these  openings  are  left  uncovered  by  the 
inner  edge  of  the  valve  head.  The  exhaust  passes 
through  the  valve  to  a  pipe  at  the  head-end  of  the 
cylinder. 

Fig.  307  is  a  cross  sectional  view  of  the  frame  show- 
ing the  construction  of  the  rock-shaft  and  cross-head, 
and  it  is  seen  that  the  rock-shaft  is  provided  with  an  oil 
pocket  for  lubricating  the  joint  of  the  lower  rocker-arm. 

In  Fig.  308  is  a  side  elevation  and  plan,  and  in  Fig. 
309  a  longitudinal  section  through  the  cross-head,  while 


7V/A-  IDE  ENGINE. 


f       THElDtENEINE 


t'uj.    303. 


THE  IDE  UNQ1NE. 


Of  THt 

UNIVERSITY 

OF 


200 


MODL'RX  NTl'JAM  FJXG1NES. 


201 


Fig.  .Ill)  is  an  end  section,  and  Fig.  311  an  end 
elevation  of  the  Imsh. 

Tin'  pin  is  central  in  the  i.  and  is  tapered  at 

one  end. 

The  Imsh  is  cut  through  in  one  place  ami  nearly  so  in 
tWO  Other  equidistant  places,  and  is  tapered  on  us  exter- 
nal diameter,  so  lliat  by  means  of  the  nut.  it  may  lie 
drawn  within  the  cross-head  and  closed  upon  the  pin. 
thus  (irmly  securing  the  latter,  while  the  arrangement 
permits  of  the  ready  removal  of  the  pin,  and  of  the 
use  of  a  solid  end  connecting-rod  with  wedge  of  full 
width  of  bearing.  A  constant  supply  of  oil  is  supplied 
to  the  wrist-pin  from  the  oiler  on  top  of  the  engine 
frame.  The  oil  being  wiped  from  the  top  guide  and 
passing  through  a  tube  in  the  top  slide,  enters  a  funnel 
in  the  connecting-rod,  and  after  passing  through  the 
bearing,  drips  to  the  bottom  of  the  cross-head  and 
passes  through  a  hole  to  the  lower  guide,  the  one 
oiler  supplying  both  slides  and  wrist-pin  bearing. 

Figs.  :>r_'and  .'il.'!  represent  the  governor  or  speed 
regulator. 

The  eccentric  K  is  attached  to  a  hanger  A,  which  is 
pivoted  to  the  wheel  at  0,  at  L  L'  are  levers  pivoted 
to  the  arms  of  the  wheel  at  a  a'. 

I. ever  L  is  attached  at  one  end  to  a  spiral  spring  S. 
while  L'  is  attached  near  one  end  to  a  similar  spring 
and  at  its  extreme  end  to  a  dash-pot  D.  Each  lever  is 
provided  with  a  weight  marked  respectively  W  and 
W.  To  these  levers  are  pivoted  at  V  and  b,  arms  B 
and  1!'  which  are  pivoted  at  ft"  to  a  pin  at  the  upper 
end  of  the  hanger  A.  The  operation  isasfollows: 

The  centrifugal  force,  generated  as  the  wheel  revolves 
by  the  unbalanced  part  of  levers  L  L',  and  by  the 
weights  W  and  W,  acting  against  the  force  of  the 
springs  S  S,  moves  the  eccentric  along  the  arc  n  n 
(whose  center  is  at  <j),  and  this  lessens  the  throw  of  the 
eccentric,  and  therefore,  the  travel  of  the  valve,  causing 
the  point  of  cut-off  to  occur  earlier  in  the  piston-stroke. 

It  is  obvious  that  as  the  wheel  speed  increases,  the 
levers  open  out,  their  extreme  positions,  and  that  of  the 
pendulum  lever,  being  marked  in  dotted  lines,  and  the 
corresponding  position  of  the  center  of  the  eccentric 
being  at  /.  e  represents  the  eccentric  center  when 
the  parts  occupy  the  positions  shown  in  the  full  lines. 

The  tension  of  the  springs  S.  is  regulated  as  follows: 


The  springs  at  their  points  of  attachment  to  the 
wheel  are  secured  jn  the  sliding  blocks  r,  Fig.  312, 
which  may  be  operated  along  the  radial  sliduways  y  by 
means  of  the  screws  whose  square  heads  are  shown  at 
It  li'.  When  the  block  T  is  in  the  position  shown  in  the 
ligtire,the  arc  in  which  the  upper  end  could  move- with- 
out further  tension  to  the  springs  is  denoted  by  the  arc 
in.  but  if  we  move  block  r  inwards  to  the  other  end  of 
slideway  y.  this  arc  would  become  arc  c,  and  it  is  plain, 
that  as  c  is  further  from  the  outer  position  x  of  the 
end  of  the  lever,  therefore,  the  spring  will  require  to  he 
extended  more,  and  will  be  placed  under  more  tension 
when  the  block  r  is  at  the  inner  than  when  it  is  at  the 
outer  end  of  the  c-lideway  g,  or,  in  other  words,  with 
the  block  r  in  the  position  it  occupies  in  the  figure,  the 
spring  S  would,  while  the  lever  L  moved  out  to  the 
dotted  lines,  be  further  extended  to  an  amount  equal  to 
the  radius  from  x  to  the  arc  m,  whereas,  with  the  block 
r  moved  by  the  screw  h  to  the  other  end  of  the  slide- 
way  y,  the  spring  S  would,  while  the  lever  moved  out 
to  x,  require  to  be  distended  to  an  amount  equal  to  the 
radius  from  arc  c  to  x,  the  radius  being  in  each  case 
measured  in  a  line  from  x  to  r,  as  denoted  by  the  dotted 
lines.  The  adjustment  to  find  the  required  position  for 
blocks  r  is  effected  by  experiment  with  the  engine  under 
light  and  heavy  loads,  with  a  speed  recorder  and  an 
indicator  attached,  so  as  to  note  the  revolutions  at 
various  points  of  cut-off. 

The  dash-pot  D  contains  glycerine,  and  consists  of  a 
case  or  barrel  containing  a  piston  and  rod,  the  latter  being 
pivoted  at  rf  while  the  barrel  is  pivoted  to  the  lever  L', 
so  that  as  the  latter  moves  outwards  towards  the 
position  denoted  by  the  dotted  lines  it  draws  the  case 
with  it.  Through  the  piston  are  the  small  holes  p  p, 
and  it  is  obvious,  that  as  the  barrel  or  case  is  pulled 
outwards,  the  glycerine  with  which  the  case  is  filled 
must  pass  through  these  holes  from  one  side  of  the 
piston  to  the  other. 

Now  if  the  motion  of  the  case  over  the  piston  is  so 
fast  that  there  is  not  sufficient  time  for  the  glycerine  to 
pass  through  the  holes  p,  then  the  glycerine  on  one  side 
of  the  piston  will  be  under  compression,  while  on  the 
other  side  there  will  be  a  partial  vacuum,  hence,  the 
action  of  the  dash-pot  is  to  offer  a  resistance  to  sudden 
vibrations,  or,  in  other  words,  to  equalize  and  steady 


202 


.MODERN  STEAM  EX <; 


the  action  of  the  speed  regulator..  Referring  now 
to  the  mechanism  for  shifting  the  eccentric  across 
the  shaft  to  alter  the  valve  travel,  and  thereby 
vary  the  point  of  cut-off,  Fig.  314  represents 
the  parts  in  the  positions  they  would  occupy  when  the 
crank  is  on  the  dead  center  B.  The  eccentric  is  shown 
shifted  inwards  to  its  position  of  least  throw,  its  center 
being  at  /  or  distant  from  the  center  C  of  the  shaft 
to  the  amount  of  the  steam  lap  of  the  valve  which  is 
supposed  to  have  no  lead. 

The  pivoted  end  C'  of  the  eccentric  hanger  is  on  the 
line  of  centers  of  the  engine,  and  if  from  C'  as  a  center 
we  mark  an  arc  //'.then  this  arc  will  represent  the 
patli  of  motion  of  the  center  of  the  eccentric  when 
moved  across  the  shaft  by  the  eccentric  hanger.  "\Vhcn 
the  eccentric  is  moved  across  the  shaft  to  its  position  of 
greatest  throw,  its  center  stands  at  e  and  the  path  of 
revolution  of  its  center  is  on  the  circle  n. 

To  find  the  position  the  upper  end  of  the  rocker-arm 
and  the  pivoted  end  of  the  eccentric-rod  must  be  in,  in 
order  that  shifting  the  eccentric  from  /  to  «  may  not 
move  the  valve,  we  set  a  pair  of  compasses  to  represent 
the  length  of  the  eccentric-rod,  and  from  e  as  a  center 
mark  an  arc  w,  and  then  with  the  same  radius,  mark 
from  /  an  arc  y,  and  where  w  and  y  intersect,  or  at  a:, 
is  the  position  for  that  end  of  the  eccentric-rod,  the 
crank  being  on  its  dead  center  B.  Now  suppose  we 
rest  the  compasses  at  a:,  and  mark  an  arc  /  c,  and  it  is 
seen  that  between  the  circles  n  and  »'  the  arcs,  /'  / 
and  c  f  practically  coincide,  and  it  becomes  clear,  that 
moving  the  eccentric  across  the  shaft  will  not  move 
the  rocker,  and  therefore,  will  not  move  the  valve. 

With  the  eccentric  center  at  /,  its  path  of  revolution 
will  be  on  the  dotted  circle  n',  and  as  the  rocker-arms 
are  of  equal  lengths,  the  travel  of  the  valve  will  equal 
the  diameter  of  circle  n',  or  equal  to  twice  the  lap, 
hence  there  would  be  no  admission  of  live  steam, 
because  the  center  of  the  eccentric  is  at  the  end  of  its 
stroke,  and  as  soon  as  the  crank  moves,  the  valve  will 
begin  to  move  back.  But  as  soon  as  the  eccentric  is 
shifted  across  the  shaft  from  /  towards  e,  there  will  be 
an  admission  of  live  steam,  beginning  when  the  crank 
passes  its  dead  center,  and  the  period  of  this  admission 
depends  upon  the  amount  the  eccentric  has  been  shifted 
across  the  shaft  by  the  governor  or  speed  regulator. 
Suppose  then,  that  the  eccentric  center  is  shifted  from 


UNIVERSITY 


\ 


203 


204 


MODERN  STEAM  ENGINES. 


f  to  e'  so  as  to  give  the  longest  period  of  admission  or 
latest  point  of  cnt-off,  and  we  may  find  at  what  point 
in  the  piston-stroke  this  occurs,  as  follows:  As  the 
crank  motion  is  in  the  direction  denoted  by  the  arrow, 
the  eccentric  will  move  from  e  to  e',  the  cut-off  occur- 
ring when  it  arrives  at  e'.  The  degrees  of  angle  it 
moves  through,  from  the  point  of  admission  to  the  point 
of  cut-off,  is  shown  on  the  crank-pin  circle  at  E  E',  and 
it  is  obvious  that  the  crank  will  move  through  the  same 
angle,  hence  we  take  the  length  of  arc  E  E',  and  mark 
it  from  B,  thus  getting  at  B'  the  crank  position  at  the 
time  the  cut-off  occurs. 

"VVe  then  set  a  pair  of  compasses  to  represent  the 
length  of  the  connecting-rod,  and  from  B  mark  an  arc 
at  i,  and  from  D  mark  an  arc  d,  thus  marking  from  b  to 
d  on  the  line  of  engine  centers,  the  length  of  the  piston 
stroke;  with  the  same  set  of  compasses  mark  from  B' 
an  arc  q,  and  from  where  q  cuts  the  line  of  centers, 
erect  a  perpendicular  line  r,  which  in  its  distance  from 
perpendicular  line  J,  gives  us  the  longest  period  of  live 
steam,  or  in  other  words,  the  latest  cut-off,  as  marked 
in  the  figure,  and  it  is  thus  found  that  the  governor,  in 
shifting  the  eccentric  across  the  shaft  from  f  to  e, 
varies  the  point  of  cut-off  from  about  three-quarter 
stroke  to  no  admission. 

In  practice,  however,  the  rock-shaft  center  is  lowered 
sufficient  to  bring  the  apex  of  its  upper  arm  7°  below 
the  line  of  engine  centers,  as  shown  in  Fig.  3 1 6.  This 
causes  the  admission  to  begin  when  the  crank  passes  the 
line  of  the  eccentric-rod,  and  gives  -fa  inch  lead  when 
the  crank  is  on  the  dead  center. 

Obviously  therefore,  under  these  conditions  the 
point  of  admission  varies  for  the  different  points  of 
cut-off,  and  fnrthermore,  in  proportion  as  the  eccen- 
tric is  shifted  out  towards  e  for  longer  points  of  cut-off, 
the  lead  increases,  because  the  eccentric,  having  a 
greater  throw,  moves  the  valve  more  during  a  given 
number  of  degrees  of  eccentric  motion.  The  increase 
of  lead,  however,  at  the  later  points  of  cut-off,  serves 
to  compensate  for  the  lesser  amount  of  compression  at 
the  later  cut-offs  and  thus  serves  to  equalize  the 
amount  of  cushioning  on  the  piston. 

It  is  obvious,  however,  that  in  this  case  the  shortest 
point  of  cut-off  will  not  occur  until  the  piston  has 
moved  past  the  dead  center  enough  to  move  the  valve 


a  distance  equal  to  the  amount  of  the  lead.  It  will 
be  observed  that  there  is  an  offset  in  the  rocker- 
arms,  and  the  object  of  this  offset  is  to  cause  the 
valve  to  move  the  fastest  when  the  piston  is  moving 
the  fastest,  and  thus  proportion  the  admission  to 
the  piston  speed.  To  investigate  this,  we  proceed 
as  in  Fig.  315,  in  which  the  parts  are  shown  in 
the  positions  they  would  occupy  with  the  crank  on  the 
dead  center  B,  and  the  eccentric  shifted  across  the 
shaft  to  its  position  of  greatest  throw  at  e,  for  the  latest 
point  of  cut-off. 

Now,  while  the  eccentric  moves  from  e  to  r,  the  valve 
will  move  to  open  the  port  for  the  admission  of  steam, 
and  while  it  is  moving  from  r  to  e',  the  valve  will  be 
moving  to  close  the  port,  the  cut-off  occurring  when 
the  eccentric  reaches  e'.  During  this  period  of  eccen- 
tric motion,  the  upper  rocker- arm  will  move  from  TO  to 
n,  opening  the  port,  and  then  back  to  m,  closing  it  for 
the  cut-off,  while  the  piston  will  move  from  the  head- 
end towards  the  crank-end  of  the  cylinder. 

Now  suppose  the  crank  to  be  on  the  other  dead 
center,  and  the  eccentric  will  be  at  g,  and  the  upper 
rocker-arm  at  p,  then  while  the  eccentric  moves  from  g 
to  Ti,  the  upper  rocker-arm  will  move  from  p  to  u,  opening 
the  steam  port,  and  while  the  eccentric  moves  from  h  to  k 
the  upper  arm  will  move  from  u  to  p,  and  the  cut-off 

will  occur. 

When  the  rocker-arm  is  at  n,  the  lower  arm  is  at  n'; 

when  the  upper  is  at  p,  the  lower  is  at  p',  and  so  on; 
and  if  we  draw  a  line  beneath  the  lower  rocker-arm,  we 
may,  by  means  of  the  vertical  lines  n'  m',  etc.,  trace  the 
movement  of  the  valve,  thus  when  the  crank  is  moving 
from  D,  the  valve,  in  opening  for  the  admission,  moves 
a  distance  equal  to  radius  m'  n',  whereas,  during  the 
admission  for  the  other  stroke,  it  moves  the  lesser 
radius  from  p'  to  u',  and  we  have,  therefore,  that  dur- 
ing the  period  of  admission  while  the  crank  moves 
from  D,  the  valve  moves  faster  than  it  does  for  the 
admission  period  when  the  crank  moves  from  B,  and  it 
follows  that  since  the  piston  moves  faster  during  the 
live  steam  period  from  D,  than  it  does  for  the  cor- 
responding period  from  B,  therefore  the  valve  motion 
is  timed  with  the  piston  motion,  giving  a  quicker 
admission  for  the  port  at  the  crank-end  than  for  that 
at  the  head-end  of  the  cvlinder. 


<o 

VI 

CO 


r 5. 


205 


206 


MODERN  8TEAX  ENGINES. 


The  Westinghouse  Engine. 


Figs,  from  317  to  324,  represent  the    Westinghouse 
Automatic  Cut-off  Single-acting   Engine. 
Fig.    317  is  a   front,  and    Fig.  318  a  rear   view   of  the 
engine,  while  tig.  319  is  a  sectional  view  on  a  vertical 
plane   passing   through   the  center   of  the  crank-shaft 


are  trunk  pistons,  the  wrist-pin  b,  for  the  upper  end  of 
the  connecting-rod,  passing  centrally  through  the  piston. 
Kach  piston  has  four  packing-rings  to  maintain  it 
steam  tight,  and  is  made  long  enough  to  form  its  own 
guide  in  the  cylinder  bore,  thus  dispensing  with  the 
usual  guide-liars  and  cross-head.  The  upper  end  of 
each  piston  is  chambered  (as  seen  in  the  left  hand 
piston,  which  is  shown  in  section)  to  prevent  condensa- 
tion. The  cranks  are  set  exactly  opposite  to  each  other 
so  that  one  piston  is  always  in  action,  and  the  live  steam 


Fig.  317. 


bearings,    and   Fig.   320  a  sectional   view,  through  the 
cylinder  in  a  plane  at  a  right  angle  to  the  crank-shaft. 

There  are  two  steam  cylinders  A  A  having  covers  a  a 
nt  their  upper  ends  only,  the  lower  ends  being  open  for 
the  connecting-rod  to  work  through.  The  pistons  D  D 


period  in  one  cylinder,  corresponds  to  a  certain  portion 
of  the  exhaust  period  in  the  other,  this  period  depend- 
ing upon  the  point  at  which  the  cut-off  occurs. 

The  upper  end  of  the  connecting-rod  is  bushed   with 
a  thimble,    while  at  the  crank-end  it  is  provided  in  the 


'  -IFONNIA 


Til  /•:  1  1  ' 


upper  half  of  the  bore  for  the  crank-pin  with  an  anti- 
friction metal  lining,  this  being  the  la  (on  ac 
count  of  the  steam  acting  on  one  side  only  of  the 
piston)  always  under  \".  pressiiui,  wliilo  tiie 
other  half  performs  no  duty. 

The  cranks  are  balanced  by  the  over-hanging  [>i' 
bob  i.      The   cylinder  covers  are    provided  with  what  is 
termed     a   pup-nut     head,    the    construction     being      u 
follows:     The   renter   of  the   inside  cvlinder-head,  Fig. 
321,  is  a  separate   piece,   screwed    or  driven    into   place 


i-:  i-:.\  <  ;  i  .v  /•; 


207 


mentally  determined)  to  crack  out  when  a  pressure  of 
'JOD  pounds  per  square  inch  is  reached. 

It',  therefore,  the  engine  cylinder  should  receive  a 
charge  of  water,  the  center  piece  will  break  out.  thus 
relieving  tin;  pressure  and  preventing  the  breakage  of 
parts  that  would  lie  more  costly  to  repair  or  replace. 

The  construction  of  the  main  bearings  is  seen  in 
the  sectional  view,  Fig.  319.  The  crank-journal  II  is 
taper,  and  works  in  a  shell  d  lined  with  Babbitt  metal. 
Between  the  flange  of  the  shell  d  and  the  cover  d'  ia  a 


Fig.  318. 


against  a  shoulder,  a  a.  .It  is  prevented  from  any  pos- 
sibility of  getting  into  the  cylinder  by  the  indicator 
plug  h,  which  draws  it  up  to  the  loose  outer  head  c  c. 
This  confer  piece  is  partly  cut  away  on  the  upper  side 
by  a  circular  grove  d  d.  leaving  metal  enough  (experi- 


chamber,  containing  a  ring  wiper  W,  which  takes  tip 
the  oil  as  it  works  past  the  bearings,  and  returns  it 
through  the  tube  e  to  the  crank  case  C,  which  is  partly 
died  with  water,  upon  which  floats  a  layer  of  oil  for 
lubricating  the  cranks  and  eccentrics,  as  will  be  ex- 


20S 


MODERN  STEAM  ENGINES. 


plained  presently.  Collar  washers  t  t,  Fig.  319,  of 
bronze  form  the  end  bearings  of  the  cranks,  and  lead 
washers  v  prevent  the  taper  sleeves  from  being  forced 
up,  so  as  to  cause  binding  on  the  crank-journals  H.  A 


9 


filled  with  live  steam.  In  the  position  the  parts  occupy 
in  the  figure,  steam  is  about  to  be  admitted  to  the  cylin- 
der through  the  annular  port  P,  which  is  left  open  for 
the  admission  by  the  upward  motion  of  the  valve,  the 


Fig.  319. 


center-bearing  K    bridges  the  crank  case,  and   receives 
the  downward  thrust  of  the  crank  at  H. 

The  construction  of  the  valve  mechanism  is  shown  in 
Pig.  322.  which  is  a  vertical  section  through  the  central 
plane  of  the  valve  chest,  and  it  is  seen  that  a  piston 
valve  V,  having  four  packing-rings,  is  employed.  Steam 
is  admitted  to  the  central  portion  S,  which  is  constantly 


eccentric  I  moving  from  right  to  left.  The  exhaust 
for  this  cylinder  is  taking  place  through  the  annular 
exhaust  port  p'  p'.  which  is  also  opened  by  the  up- 
ward motion  of  the  valve.  The  valve  is  situated 
between  the  two  steam  cylinders,  and  the  one  valve, 
therefore,  serves  for  both  cylinders,  the  exhaust  for  the 
other  cylinder  entering  the  chamber  above  the  valve. 


Till-:   \\'f-:sTl\<;/lnrsf-;  EN 


20!) 


passrng    through  the  valve  to  the   vxh;ai-t   \>i\«'   n. 


.•ilvc  works  in  ii  .  which  may  be  replaced 


Fig.  32(3 
The  valve  is  guided  by  a  piston  guide  J,   which  being 


Fiy.  321. 

covered,    prevents  the   exhaust   from  passing  into  the 
lower  part  of  the  casing  in   which  the  crank   works. 


Fig.  322. 

by  a  new  one  when  necessary  to  restore  the  fit  of 
the  valve. 

The  construction  of  the  governor  for  varying  the 
point  of  cut-off  by  moving  the  eccentric  across  the 
shaft  to  reduce  the  throw  of  the  eccentric,  and  there- 
fore the  travel  of  the  valve,  is  as  follows:  The  disc  A 
A .  Fig.  32  5,  is  cast  solid,  and  keyed  to  one  of  the 
cranks. 

The  loose  eccentric  C,  is  suspended  by  the  arm  e, 
from  the  pin  tl,  around  which  it  lias  a  motion  of  adjust- 
ment; B  B  are  the  Governor  Weights,  pivoted  on  the 


210 


MODERN  STEAM  ENGINES. 


pins  b  b;  one  of  the  weights  is  connected  to  the  eccen- 
tric by  the  link  f,  and  both  weigths  are  connected  to 
operate  in  unison  by  the  link  e.  Coil  Springs  D  D  fur- 
nish the  centripetal  or  returning  force.  The  eccentric 
encircles  the  shaft  S,  the  opening  being  elongated  to 
admit  of  the  proper  motion.  The  stops  s  s  limit  the 
motion  of  the  weights. 

In  Fig.  223  the  Governor  Weights  are  shown  in  the 
position  of  rest,  whereby  the  eccentric  is  thrown  over  to 
its  position  of  greatest  eccentricity,  giving  a  maximum 
travel  to  the  valve,  corresponding  to  a  cut-off  of  about 


|  stroke.  The  parts  of  the  governor  remain  in  this 
position  until  the  engine  is  within  a  few  revolutions  of 
its  full  speed.  The  centrifugal  force  of  the  weights 
then  over-balances  the  tension  of  the  springs,  and  the 
weights  move  outward,  reducing  the  travel  of  the 
eccentric  and  valve,  and  consequently  shortening  the 
point  of  cut-off. 

The  extreme  outward  position  of  the  weights  is 
shown  in  Fig.  324.  The  cut-off  for  this  position  occurs 
so  early  as  to  barely  hold  the  engine  up  to  speed  when 
running  without  load. 

When  the  engine  is  properly  loaded,  so  as  to  cut  off 


from  |  to  £  stroke,  (at  which  the  engine  developes  its 
rated  power)  the  position  of  the  parts  is  mid-way  be. 
tween  the  two  positions  shown.  The  position  to  which 
the  governor  must  move  the  eccentric  in  order  to  cut 
off  the  steam  at  a  given  point  in  the  stroke,  may  be 
found  by  the  construction  explained  with  reference  to 
figures  278,  279  and  280,  and  the  port  openings,  by 
the  construction  explained  wtih  reference  to  Fig.  225, 
while  the  valve  lead  and  points  of  admission  may  be 
considered,  as  was  done  with  reference  to  Fig.  227. 
The  means  provided  for  lubricating  the  various  worV. 


Fig.  324. 

ing  parts  without  the  use  of  oil  cups,  are  as  follows: 
A  reservoir  0,  Fig.  322,  contains  a  supply  of  oil, 
which  is  admitted  from  time  to  time  through  the  cap  at 
q.  From  the  oil  reservoir  are  pipes  having  the  globe 
valves  1 1,  Fig.  319,  which  may  be  operated  to  feed  oil 
into  the  receptacles  /  /  Fig.  319,  the  oil  passing 
thence  to  the  crank-shaft  journals  H,  and  after  finding 
its  way  to  the  ends  of  these  journals,  it  is  carried  into 
the  case  or  chamber  C,  Figs.  319  and  320,  in  which  the 
crank  works.  This  case  is  enclosed  by  the  cover  shown 
at  h  in  Fig.  320,  and  contains  water  whose  level 
nearly  reaches  the  crank-shaft;  floating  upon  this  water 


THE 


Xi;  HOUSE  ENG1XE 


211 


is  a  layer  of  oil.  into   which   the  cranks   ami    eereir 
dip  during  the  lower  part  of  their  path  of  revolution, 
thus  giving  constant  lubrication. 
To' maintain  the  proper  level  of  water  in  the  case  C, 

a  drip-pipe   V.  Fijr  .'I'-"-',  is    provided,  which  admits  the 

of  condensation   from  the  exhaust  steam. 
Similarly,  either  additional  water  or  oil  for  the  case 
C,  may  be  admitted  through  the  pipe  R  H.  Imt  it  is  ob- 


3 1 9,  prevents  the  accumulation  in  the  case  of  water 
above  the  level  of  the  top  of  the  pipe  e,  and  being  con- 
nected to  the  bottom  of  the  case,  it  carries  off  the  sur- 
plus water  only,  maintaining  the  level  of  the  oil  at  & 
constant  height  in  the  case. 

This  level  is  indicated  by  the  height  of  the  water  in 
the  funnel-head  n,  and  is  required  to  be  such  that  the 
water  is  always  in  sight. 


Fig.  325. 

The  James  and  Wardrope  Engine. 


vious,  that  by  a  proper  adjustment  of  the  valves  at  1 1, 
Fig.  319,  the  oil  supply  may  be  made  sufficiently  con- 
stant from  the  reservoir  0,  Fig.  322,  to  render  it  un- 
necessary to  resort  to  the  pipes  R  R,  for  any  additional 
supply. 

A  siphon  over-flow,   having  a  funnel  head  at  n,   Fig. 
27 


The  MiMi- Cylinder  Engine. 


In  this  class  of  steam  engine  there  are  two  or  more 


OF  THE 

(UNIVERSITY, 
\^CA 


212 


MODERN  STEAM-  ENGINES. 


steam  cylinders,  whose  axial  lines  usually  radiate  from 
the  center  of  the  crank-shaft.  These  cylinders  are 
single  acting,  or  in  others,  receive  steam  at  the  head- 
end only,  the  other  end  being  open,  hence  the  connect- 
ing-rods are  under  compression,  only  being  pushed  by 
the  piston  and  not  pulled  during  the  return  piston- 
stroke,  and  the  journal  pressure  always  being  in  the 
same  direction  at  both  ends  of  the  connecting-rod,  the 


Fig.  326. 

cross-head  journal,  crank-pin  journal,  and  main-shaft 
journals  are  kept  seated  on  one  side  only  of  their  bear- 
ings, hence  the  wear  does  not  cause  play  or  lost  motion, 
and  delicate  adjustments  of  fit  are  not  necessary  in 
order  to  prevent  pounding  or  thumping. 

Figs.  325  and  326  represent  the  James  and  "Ward 
rope,  three  cylinder  single-acting  engines,  these  engrav- 
ings being  extracted  from  Engineering. 

The  center-lines  of  the  three  cylinders  radiate  from 


the  center  of  the  crank-shaft,  and  their  connecting-rods 
all  attach  to  the  same  crank-throw,  which,  therefore, 
has  no  dead  center.  Each  cylinder  has  a  separate 
piston-valve  which  works  in  a  line  parallel  to  the  cylin- 
der bore,  and  is  operated  from  a  rod  driven  by  the 
neighboring  piston,  as  is  plainly  seen  in  the  engraving. 

The  ends  of  each  piston-valve  are  enlarged,  and  are 
provided  with  packing-rings.  The  live  steam  enters  at 
the  section  of  reduced  diameter  between  the  enlarged 
ends,  the  position  of  the  steam  pipe  being  shown  in  the 
dotted  circles  in  Fig.  325.  The  steam  enters  the  cylin- 
der at  its  upper  end,  when  the  port  is  uncovered  by  the 
motion  of  the  valve  towards  the  head-end  or  outer  end  of 
the  cylinder,  and  exhausts  when  the  piston-valve  has 
moved  sufficiently  towards  the  crank  to  leave  the  port 
uncovered,  at  which  time  the  steam  passes  the  end  of  the 
valve,  and  finds  exit  to  the  exhaust  pipe,  at  the  outer 
end  of  the  bore  in  which  the  valve  works.  This  part 
of  the  exhaust  is  therefore,  controlled  by  the  valve,  but 
there  are  supplementary  exhaust  ports  which  are  not  so 
controlled,  these  latter  being  shown  in  the  dotted  open- 
ings in  Fig.  325,  and  also  in  section  in  Fig.  326;  these 
ports  are  merely  uncovered  by  the  piston  as  it  passes  them 
and  are  situated  so  as  to  come  into  action  when  the  piston 
lias  made  about  f  of  its  stroke  towards  the  crank  and 
permits  of  the  escape  of  a  large  proportion  of  the  steam. 

The  point  at  which  the  piston-valve  effects  its  ex- 
haust, depends  upon  the  point  at  which  the  end  of  the 
valve  effects  the  compression  by  closing  the  steam  port, 
the  action,  in  this  respect, '  being  precisely  the  same  as 
that  explained  with  reference  to  Figs.  271  and  272 
concerning  the  piston  valve  of  the  Armington-Sim's 
engine,  it  being  noted,  however,  that  in  this  case 
the  valve  is  single  ported  only.  .  Both  the  exhausts 
enter  the  casing  in  which  the  crank  revolves,  this  casing 
forming  an  enclosed  chamber  having  the  main  exhaust 
pipe  at  its  bottom.  The  exhaust  steam  therefore 
excludes  the  air  from  contact  with  the  pistons,  and 
thereby  prevents  the  loss  of  heat  which  would  other- 
wise occur. 

The  pistons  are  made  long,  and  are  trunks,  the  con- 
necting-rods pivoting  to  their  outer  ends,  thus  giving 
a  long  connecting-rod  and  dispensing  with  the  use  of 
guides,  the  long  pistons  and  cylinder  bores  serving  for 
guides,  as  is  also  the  case  with  the  valves. 


214 


MODERN  STEAM  ENGINES. 


N.  Y.  Safety  Steam  Power  Go's.  Engine. 

Pig.  327  represents  an  Automatic  Cut-Off  Engine, 
by  the  New  York  Safety  Steam  Power  Co.  The  gov- 
ernor is  of  the  usual  wheel-regulator  construction  and 
operates  a  piston  valve,  which  takes  steam  at  the  ends 
and  exhausts  it  in  the  middle  of  its  length.  1  n  order 
to  perfectly  balance  the  valve,  the  diameter  at  the 
valve-rod  end  is  made  sufficiently  larger  than  the  head- 
end, to  make  the  area  exposed  to  the  steam,  equal. 


TJie  Ball  Automatic  Cat-Off  Engine. 

In  the   Ball  Automatic  Cut-Off  Engine,  the  point  of 


view  of  the  engine,  Fig.  329  represents  the  governor 
with  the  eccentric  removed,  and  Fig.  324,  the  eccentric. 
An  arm  T  T  is  keyed  to  the  crank-shaft,  and  upon 
the  hub  of  this  arm  the  pulley  is  a  working  fit,  so  that 
it  can  revolve  a  certain  amount  upon  the  arm.  This 
amount  is  limited  by  means  of  two  lugs  which  project 
into  cavities  provided  in  the  end  of  the  arm  hub,  as 
seen  in  Fig.  329,  The  governor  balls  are  pivoted,  by 
arms  to  the  pulley  arms,  as  shown,  each  of  these  arms 
being  connected  to  two  spiral  springs,  of  which  one  is 
fast  to  tlTe  inside  rim  of  the  pulley,  and  the  other  is 
fast  to  the  lever  T.  Now  suppose  the  pulley  to  revolve 
against  a  steady  resistance,  offered  by  the  belt  to  the 
pulley,  and  the  balls  will  swing  out  and  revolve  in  a 
circle  of  such  a  diameter  as  will  create  an  equilibrium 


Fifj.  328. 


cut-off  is  varied  by  a  wheel  governor  shifting  the  eccen- 
tric across  the  shaft.  A  flat  valve  is  used  which  gives 
a  double  port  opening  through  a  single  port,  the 
construction  being  as  follows:  Fig.  328  is  a  general 


between  the  centrifugal  force  generated  by  the  balls, 
and  the  centripetal  force  of  the  four  spiral  springs. 
Suppose,  however,  that  the  belt  resistance  suddenly 
increases,  and  any  retardation  of  the  pulley  wheel  re- 


////•;  jiM.i.  .1 1'j'i/MA  TIC  CUT-OFF  I:.\<;I.\E.  215 

pulling  from  the  increase  of  load,  will  at  once  be  com-  |  be  moved  across  the  shaft  into  position  to   give  later 


OPTM 

UNIVERSITY, 


Fig.  329. 


municated  to  the  weight  arms,  nnd  the  weights,  increas- 


Fig.  330. 
ing   the  centripetal  force,  will   cause  the   eccentric   to 


points  of  cut-off,  and  increase  the  power  of  the 
engine  to  a  decree  corresponding  to  the  amount  of  in- 
creased resistance  offered  by  the  belt  to  the  pulley. 
The  governor  action  is  here,  then,  independent  of  the 
crank-shaft,  which  may  go  on  at  its  regular  speed.  By 
this  construction  therefore,  it  is  necessary  to  change 
the  speed  of  the  crank-shaft  and  fly-wheel  before  the 
governor  can  act,  since  the  latter  takes  a  short  cut,  as  it 
were,  and  acts  directly  upon  the  valve  without  refer- 
ence to  the  fly-wheel  and  crank-shaft. 


THE  ECCENTRIC  CONSTRUCTION. 

The  construction  of  the  eccentric  mechanism  is 
shown  in  Fig.  330,  in  which  A  is  the  main  eccentric 
having  an  elongated  opening,  which  permits  it  to  swing 
across  the  shaft.  To  this  eccentric  is  secured  the  arm 
B,  which  is  pivoted  upon  the  pin  Y  of  arm  or  lever  T 
in  Fig.  3'J9,  thus  allowing  the  eccentric  a  pendulum 
motion  across  the  crank-shaft. 


216 


MODERN  STEAM  ENGINES. 


The  amount  of  this  pendulum  motion  is  controlled 
by  the  rotation  of  a  disc  C.  This  disc  has  a  flange  D, 
which  is  eccentric  to  the  crank-shaft,  and  on  the  inside 
of  this  eccentric  flange  is  a  ring  E,  which  lias  a  stud  F 


Fiy.   331. 


332  and  333.  It  is  made  in  two  parts  T  and  S  having 
rectangular  flat  faces,  and  an  annula-r  ring  flange  at  the 
back. 

The  flange  of  T  fits  within  that  of  S  and  is  provided 
with  two  spring  snap  rings  to  maintain  a  steam  tight 
(it.  The  live  steam  enters  the  inside  of  the  valve,  and 
pressing  against  the  projecting  lips  and  of  the  end  faces 
of  the  rings,  moves  the  two  halves  of  the  valve  apart 
and  up  against  the  seat  faces.  The  valve  is  thus  re- 
lieved of  pressure  upon  that  part  of  its  area  which 
forms  the  openings  through  which  the  live  steam  enters. 

The  steam   ports  are  so   shaped,  as  to  receive  steam 


engaging  with  the  main  eccentric  A,  as  shown. 

The  rotation  of  the  disc  upon  the  crank-shaft  there- 
fore causes  the  main  eccentric  to  swing  across  the  shaft, 
from  the  pin  Y,  as  a  center  of  motion.  The  disk  D 
also  has  sleeves  encircling  the  shaft,  and  projecting 
through  the  elongated  bore  of  the  main  eccentric,  and 
on  the  end  of  this  sleeve  is  a  ring-nut  G  which  holds 
all  the  parts  in  place. 

The  disc  is  rotated  around  the  crank-shaft  by  means 
of  two  pins  in  its  back  face,  which  fit  into  the  holes 
shown  in  the  ends  of  the  links  shown  in  Fig.  329  to  be 
pivoted  at  their  ends  to  the  governor  balls. 

TH*    SLIDE-VALVE. 

The  construction  of  the  valve  is  shown  in  Figs.  331, 


Fi'j.  333. 

from  the  port  openings  given  by  both  halves  of  tho 
valve,  the  course  of  the  steam  being  denoted  by  the 
arrows  in  Fig.  333,  where  it  is  seen  that  the  exhaust 
passes  out  at  the  ends  of  the  valve. 


THE  DEXTER  /•.'.V'7/.V/:. 


217 


218 


MODERN  STEAM  ENGINES. 


ffl 


TIII-:  DEXTER  t-:.\i;iM-;. 


219 


TJie  Dexter  Automatic  Cnt-Oj)'  Engine. 


In  the  Dext6?  engine  (Fig.  334),  a  !l.-ii  palre  driven  1>\- 
a  fixed  eccentric,  and  that  is  balanced  through  tin'  greater 
part  of  its  Stroke,  controls  the  admission  and  exhaust. 
hence  the  lead  and  tin-  [mints  of  release  are  equal  for 


rod  for  the  main,  and  K  that  for  the  cut-ofl  valve.  The 
auxiliary  steam  chest  C  is  suspended  from  the  walls  of 
the  main  steam  chest,  and  receives  steam  at  the  center. 
In  Fig.  336  is  given  an  end  view  of  the  steam  chest 
and  valves,  showing  the  method  of  susper*".  ing  the 
auxiliary  steam  chest  within  the  main  steam  chest,  and 
enaliling  it  to  set  up  to  take  up  the  wear  between  it  and 
the  back  of  the  main  valve. 


. 

r 


Fig.  336. 
The  Dexter  Automatic  Cut-Off  Engine  — The  Valve  Construction. 


all  points  of  cut-off.  Fig.  335  is  a  longitudinal  section 
of  the  valves,  ~L  L  are  the  cylinder  steam  ports,  'and 
M  M  the  exhaust  ports.  On  the  back  of  the  main 
valve  F  is  a  piece  C,  which  acts  as  a  pressure  plate  for 
the  main  valve,  and  receives  a  double-ported  piston 
valve  D,  whose  ports  are  shown  at  J,  J,  J,  J.  G  is  the 
28 


Openings  lead  from  the  central  supply  to  the  differ- 
ent points  on  the  cut-off  valve  D,  where  admission 
occurs  through  the  ports  J,  J,  J,  J,  in  the  auxiliary  steam 
chest. 

It  will  be  seen  that  the  steam  from  the  central  open- 
ings in  the  cut-off  valve  is  distributed  to  the  main  valve 


220 


MODERN  STEAM  ENGINES. 


through  two  ports  provided  on  each  side  of  the  center 
of  the  cut-off  valve.  The  auxiliary  steam  chest  may 
be  moved  up  to  the  main  valve  to  take  up  the  wear. 
The  eccentric  C  Fig.  337,  is  pivoted  at  D.  The  weights 
E  E,  are  pivoted  at  G  G,  and  are  drawn  inwardly  by 


which  position  it  will  hold  the  eccentric  rigidly  against 
the  resistance  of  the  valve  and  its  connections.  When 
the  weights  are  in  their  extreme  inward  positions,  the 
opposite  link  will  be  in  line  with  the  points  G,  H,  I,  and 
the  eccentric  held  rigidly  against  resistance,  as  in  the 


Fig,  337. 
The  Dexter  Engine The  Construction  of  the  Governor. 


the  springs  F  F,  while  they  are  connected  to  the  eccen- 
tric by  links  with  bearings  at  H  I.  The  weights  are 
shown  in  their  extreme  outward  positions,  and  it  will 
be  seen  that  one  of  the  links  is  in  a  straight  line,  on 
the  points  G,  H,  I,  which  is  tangent  to  the  eccentric,  in 


extreme  outward  position.  Between  these  two  points 
the  resistance  is  effected  by  the  action  of  both  links. 
The  rigidity  at  the  extreme  inward  position  gives  a 
capacity  to  start  the  valve,  even  though  from  disuse 
it  may  have  become  rusted  or  gummed  to  its  seat. 


/•///•;  iu-:v.\»i.i>s  CORLISS  ENGINE. 


221 


MODERN  STEAM  ENGINES. 


a 


.3 


i  : 


Till-:  REYNOLDS  CORLISS  /•: \ ( ;  1  \ /•:. 


223 


TJie  Corliss  Automatic-  Cut-Off  Engine. 


Tin-  ('iii-ii.-s  engine  is  the  most  prominent  and  impor- 
taut  of  all  that  class  of  engines,  in  which  the  connec- 
tion between  the  eccentric-rod  and  the  valvo  stein  is 
broken,  in  order  that  the  valve  may  lie  closed  quickly 
ti.  etTect  the  rut-off,  which  occurs  at  a  point  in  the 
stroke;  that  is  determined  l>y  the  governor. 

The  (list inguishing  features  of  a  Corliss  engine  are 
the  triji  mechanism  for  releasing  the  valve;  and  its 
connection  with  the  governor;  the  dash-pot  or  its  equiv- 
alent for  closing  the  valve  without  jar  or  shock;  and 
the  wrist  motion  which  reduces  the  motion  of  the  valve 
after  it  has  opened  the  steam  port. 

There  are  two  adinisssion  and  two  exhaust  valves 
driven  by  a  single  and  fixed  eccentric,  hence  the  lead 
and  the  points  of  release  or  exhaust  are  maintained 
equal  for  all  points  of  cut-off. 


TJie  Reynolds  Corliss  Engine. 

A  representative  of  advanced  practice  in  the  Corliss 
type  of  engine,  is  given  in  Figs.  338  and  339,  which  re- 
present the  Reynolds  Corliss  Engine.  Figs.  340  and 
'!  1 1  represent  the  valve  gear  with  the  parts  in  the  posi- 
tion they  occupy  when  the  cut-off  occurs  at  half -stroke, 
the  piston  having  moved  from  the  head-end  of  the  cyl- 
inder. In  Figs.  342  and  343  the  parts  are  shown  in 
position  with  the  crank  on  the  dead  center,  and  the  piston 
at  the  crank-end  of  the  cylinder,  valve  v  having  opened 
its  port  to  the  amount  of  the  lead. 

Referring  to  Fig.  340  motion  from  the  eccentric  is 
imparted  by  the  rod  M  to  the  wrist  plate  Y,  to  which  are 
connected  the  rods  C  C'  for  operating  the  admission 
valves,  whose  spindles  are  seen  at  S  S',  and  the  rods 
F  F'  for  operating  the  exhaust  valves,  whose  spindles 
are  seen  at  T  T'. 

THE  VALVE  GEAR. 

The    mechanism   for  the  steam  or  admission   valves 


may  be  divided  into  three  elements;  first,  that  for  oper. 
ating  the  valve  to  open  the  port  for  admission;  second, 
that  for  closing  the  valve  to  effect  the  cut-off;  and  third, 
that  which  determines  the  point  in  the  stroke,  at  which 
i  be  cut-oil  shall  occur. 

The  first  consists  of  the  rod  M,  wrist  plate  Y,  and 
the  rods  C  and  C',  which  operate  the  bell-cranks  r  r 
/•'  / '  which  are  fast  on  the  valve  spindles  S  S'.  Upon  the 
ends  of  bell-cranks  r  r,  r'  r',  are  pivoted  latch  links  u  u' 
which  have  in  them  a  recess  for  the  latch  blocks,  of 
which  onp  is  seen  at  e  (the  rod  R'  and  its  connection 
with  the  valve  stem  being  shown  broken  away  to  ex- 
pose e  to  view).  During  the  admission  the  latch  block 
abuts  against  the  end  y  of  the  recess  w  and  is  tripped 
therefrom  by  the  cam  n'.  The  ends  of  arms  g  of 
the  latch  links  abut  against  the  hub  of  the  arms  d  d', 
upon  which  are  earns  n,  n'  and  at  a  a'  are  springs  for 
keeping  the  ends  g  of  latch  links  u  u'  against  the  hubs 
and  cams  of  d  d'. 

Referring  now  to  the  valve  mechanism  at  the  head- 
end only,  suppose  the  piston  to  be  at  the  head-end 
of  the  cylinder,  and  latch  block  e  will  be  seated  in  the 
recess  provided  in  it  to  receive  it,  and  as  the  bell-crank 
moves,  the  latch  block  will  be  raised  by  the  latch  link, 
which  is  carried  by  a  crank  arm  corresponding  to  that 
seen  at  x  at  the  crank-end  of  the  cylinder,  and  as  this 
crank  arm  is  fast  upon  the  valve  spindle,  the  lifting  of 
e  will  open  the  valve  for  admission.  As  soon,  however, 
as  the  end  g  of  the  latch  link  meets  the  cam  n'  the  latch 
link  will  be  moved  so  that  the  end  y  of  its  recess  will 
leave  contact  with  the  latch  block  e,  and  the  dash  pot 
will  cause  rod  R'  to  descend  ''nstantaneously  and  close 
the  valve,  thus  effecting  the  cut-off. 

THE  ADMISSION. 

The  period  of  admission,  therefore,  is  determined  by 
the  amount  of  motion  the  latch  link  u'  is  permitted  to 
have  before  its  end  g  meets  the  cam  n'  which  trips  .the 
latch  link,  and  therefore  frees  e  from  the  latch  link 
recess. 

The  point  at  which  the  cut-off  will  occur  therefore 
is  determined  by  the  position  of  the  cam  n',  because 
if  n'  is  out  of  the  way  the  end  g  of  the  latch  link  will 
not  meet  it,  the  latch  link  will  not  lisengage  from 

YlBR7*>v. 

OF  THE 

[UNIVERSITY, 

OF 


Fiij.    341. 
The  Reynolds  Corliss  Valve  Gear. 


224 


-•-  \ 


•o 


j-A 


x^Jg/// 

<y^o 

o 

<£ 

O 

o 

0> 

<t> 

o 

. 

0 

O 

0 

0 

ID 

0 

^^^o 

«M     X^^^\\\ 

TO 


225 


The  Reynolds  Corliss  Enine. 


Positions  Of  The  Parts  With  The  Crank  On  The  Dead  Center 
And  The  Piston  At  The  Crank-End  Of  The  Cylinder. 


226 


THE  REYNOLDS 

the  latch  Mock  >.  and  the  nit-ofl  would  be  effected  by 
the  lap  of  the  valve,  and  indcjx-ndently  of  the  dash-pot- 
A-.  in  Fig.  ::iO.  the  parts  are  shown  in  the  positions  thev 

py  at  the   inMant    ;  T   is  to  occur,    then 

tin'  cam  «'  has  just  tripped  the  latch  link,  and  the  end  of 

18  just  left  contact  with  the  end  y  of  the  recess  w 
in  the  latch  link  n'. 

The  point  in  the  stroke  at  which  the  tripping  of  «' 
from  e'  will  occur  and  effect  the  cut-off,  is  determined  by 
the  governor,  because  </'  is  connected  to  the  governor 
through  the  rod  G'.  In  proportion  as  the  governor 
balls  rise,  d'  is  moved  from  left  to  right,  and  the  end  of 
cam  n'  meets  :/  earlier,  or  vice  versa  in  proportion  as 
tiie  governor  balls  fall,  the  arm  d'  is  moved  to  the  left, 
;/  will  meet  the  end  of  cam  ;i'  later,  and  the  point  of 
cut-off  will  be  prolon 

We  now  come  to  tin'  means  employed  to  close  the 
valve  quickly  and  without  shock  when  the  latch  block 
is  released  from  the  latch  link.  Referring  then  to  the 
crank-end  of  tiie  cylinder,  the  latch  block  for  that  valve 
irried  upon  arm  /.  to  which  is  attached  the  rod  R 
from  th<'  piston  (the  arm  corresponding  to  x, 

but.  at  the  head-end  being  shown  removed  to  expose 
the  latch  block  to  view).  We  may  now  turn  again  to 
the  head-end  of  the  cylinder,  rod  R'  corresponding  to 
r^d  R  at  the  other  end.  and  it  is  seen  that  R'  connects 
to  a  dash-pot  piston//  having  a  stepped  diameter,  the 
]ower  half  lining  into  bore  H'.  and  the  upper  half  into 
a  bore  H.  The  piston//  (its  the  bore  H'  and  fills  it 
when  the  rod  R  is  at  the  bottom  of  the  stroke,  hence  as 
;/  is  raised,  there  is  a  vacuum  in  H'  that  acts  to  cause 
//.  and  therefore  R'  and  x,  to  fall  quickly  and  close  the 
valve  the  instant  the  latch  block  is  released  from  the 
latch  link.  To  prevent  the  descent  of  rod  R'  and  piston 
p'  from  ending  in  a  blow,  a  cushion  of  air  is  given  in 
H  by  the  following  construction: 

At  S  and  S'  are  valves,  threaded  to  screw  and  tin 
screw,  the  ends  forming  a  valve  for  a  seat  entering  H. 

As  the  I'od  R'  and  its  piston  p'  descends,  the  air  in 
II  finds  [exit  through  a  hole  at  h,  until  that  hole  is 
closed  by  the  piston  p'  covering  it,  after  which  the  re- 
maining air  in  H  can  only  find  exit  through  the  open- 
ing left  by  the  end  of  the  valve  S',  and  this  amount  of 
opening  is  so  regulated  by  the  adjustment  of  S',  that  a 

certain  amount  of  air  cushion  is  given,  which  prevents 
29 


x  /-:\t;i.\f:. 


227 


/>'  from  coming  to  rest  with  a  blow.  The  head  of  valve 
S'  is  milled  or  knurled,  and  a  spring  ('  fits,  at  its  end, 
into  the  milled  indentation,  thus  holding  it  in  its  adjust- 
ed position.  The  under  surface  of  the  upper  part  of  />' 
is  covered  by  a  leather  disc,  while  the  part  that  fits  in 
H'  is  kept  air  tight  by  a  leather  cupped  packing. 

THE    GOVERNOR    CONNECTION. 

The  connection  of  the  cam  arms  d  and  d'  with  the 
governor,  is  shown  in  Figs.  342  and  343,  in  which  the 
parts  are  shown  in  the  position  they  woirid  occupy 
when  the  crank  is  on  the  dead  center,  and  the  piston  at 
the  crank-end  of  the  cylinder.  The  rod  G'  connects 
the  cam  arm  d'  with  the  upper  end  of  lever  A,  which  is 
connected  to  the  governor,  and  vibrates  on  its  center  as 
the  governor  acts  upon  it.  • 

Now  suppose  the  speed  to  begin  to  diminish,  and  the 
governor  balls  to  fall,  and  the  direction  in  which  A  will 
move  will  be  for  its  lower  end  to  move  to  the  right, 
thus  moving  d  to  the  right,  and  carrying  its  cam  away 
from  the  end  of  the  latch  link,  which  will  therefore 
continue  to  open  the  port  for  a  longer  period  of  admis- 
sion. Or,  referring  to  Fig.  340,  it  is  plain  that  if  the 
governor  balls  were  to  lower  from  a  reduced  governor 
speed,  G'  would  move  to  the  left  and  cam  «'  would  I* 
moved  away  from  contact  with  the  end  g  of  'the  latch 
link,  which  not  being  tripped,  the  admission  would  con- 
tinue. On  the  other  hand,  suppose  the  governor  balls 
to  rise  from  an  increase  of  governor  speed,  and  d'  (Fig. 
340)  would  be  moved  to  the  right,  and  the  cam  n'  meet- 
ing 7  earlier  would  trip  e  earlier,  correspondingly  has- 
tening the  cut-off. 

The  governor  is  driven  by  a  belt  from  a  pulley  on 
the  crank  shaft  to  the  pulley  W  Fig.  342,  whose  shaft 
conveys  motion  to  the  governor  spindle  through  the 
medium  of  a  pair  of  bevil  pinions. 

THE    CONSTRUCTION    OF    THE    VALVES. 

The  construction  of  the  valves  is  shown  in  Fig.  342, 
in  which  v  represents  the  steam  or  admission  valve  for 
the  crank  end  port,  and  v'  that  for  tiie  head-end  port, 
while  v*  is  the  exhaust  valve  for  the  crank-end,  and  «*, 
that  for  the  head-end  of  the  cylinder.  All  four  valves 


228 


MODERN  STEAM  ENGINES. 


The  Reynolds  Corliss  Engine. 


Positions  Of  The  Farts  When  The  Crank  Is  On  The  Dead  Center  And  The  Piston  At  The  Crank  End. 


ij,  343. 


THE  KEYS  OLDS  CORLISS  A' 


•J-J'.i 


are  shown  in  the  positions  they  would  occupy  when  the 
crank  was  on  the  dead  center,  and  the  piston  at  the 
crank  end  of  the  cylinder,  hence  the  valve  positions 
shown,  correspond  to  the  positions  the  parts  of  the  valve 
motion  occupy  in  the  ligure. 

The  faces  of  the  valves  are  obviously  arcs  of  circles, 
of  which  the  axis  of  the  siiafts  .1  .«'  an-  the  respective 
centers.  Valve  v  has  opened  its  port  to  the  amount  of 
the  load,  which  in  this  class  of  engine  varies  usually 
from  jij  to  about  -^  inch.  As  separate  exhaust  valves 
are  employed,  the  point  of  release,  and  (as  the  same 
v.'ilve  edge  that  effects  the  release  also  effects  the  com- 
pression) therefore  that  of  the  compression,  may  be 
regulated  at  will,  by  adjusting  the  lengths  of  the  rods 
F  F',  which  have  at  one  end  a  right,  and  at  the  other 
a  left  hand  screw,  so  that  by  turning  back  the  check- 
nuts  and  then  revolving  the  rods,  their  lengths  will  be 
altered. 

Similarly  the  amount  of  admission  lead  may  be  ad- 
justed by  an  adjustment  of  the  lengths  of  rods  C  C', 
which  also  have  right  and  left  hand  screws. 

Referring  now  to  the  admission  valve  v,  it  is  seen 
that  its  operating  rod  C  is  at  a  right  angle  to  bell-crank 
r  r,  hence  the  amount  of  valve  motion  will  not  be  dim- 
inished to  any  appreciable  extent  by  reason  of  the  wrist 
plate  end  of  rod  0  moving  in  an  arc  of  a  circle,  and  the 
point  of  attachment  of  rod  C  to  the  wrist  plate  is  such 
that,  during  the  admission  the  valve  practically  gives  as 
quick  an  opening  as  though  rod  C  continued  at  a  right 
angle  to  r.  But  if  we  turn  to  valve  v ',  which  has  closed 
its  port  and  covei-s  it  to  the  amount  of  the  lap,  we  find 
that  bell-crank  C'  and  its  operating  rod  C'  are  in  such 
positions  with  relation  to  the  wrist  plate,  that  the 
motion  of  the  latter  will  have  but  little  effect  in  moving 
the  bell-crank  r1.  This  is  an  especial  feature  of  the 
Corliss  valve  motion,  and  is  of  importance  for  the 
following  reasons: 

The  lap  of  the  valve  (which  corresponds  to  the  lap  of 
a  plain  D  slide  valve)  is  usually,  in  this  class  of  engine, 
such  as  to  cut  off  the  steam  at  about  J  stroke,  but  the 
adjustment  of  the  cam  position  is  usually  so  made,  that 
from  the  action  of  the  governor,  the  latest  point  of 
cut-off  will  occur  when  the  piston  has  made  §  of  its 
stroke,  the  range  of  cut-off  being  from  this  to  an  ad  mis 
eion  equal  to  the  amount  of  the  lead. 


As  the  eccentric  is  fixed  upon  the  shaft,  the  speed  at 
which  the  valve  opens  the  port  for  the  admission  is  the 
same  for  all  corresponding  piston  positions.  Thus  sup- 
pose the  piston  has  moved  an  inch  from  the  end  of  the 
stroke,  and  the  valve  speed  will  be  the  same,  whether 
the  cut-off  in  that  stroke  is  to  occur  at  quarter-stroke, 
or  half-stroke,  and  as  the  valve  continues  to  open  the 
port  until  it  is  tripped,  therefore  at  the  moment  it  is 
tripped,  the  direction  of  valve  motion  must  be  suddenly 
reversed. 

As  the  duty  of  its  reversal  falls  upon  the  dash-pot,  it 
is  desirable  to  make  this  duty  as  light  as  possible,  which 
is  accomplished  by  the  wrist  motion,  whicli  acts  to  re- 
duce the  valve  motion  after  the  port  is  opened  a  cer- 
tain amount  for  the  admission. 

We  have,  therefore,  that  during  the  earlier  part  of 
the  admission,  the  port  opening  is  quick,  because  of  the 
eccentric  throw  being  a  maximum,  while  during  the 
later  part  of  the  port  opening,  this  rapid  motion  is  off- 
set or  modified  by  the  wrist  motion,  thus  lessening  the 
duty  of  the  dash-pot  and  enabling  it  to  promptly  close 
the  valve. 


VABYINO  THE  ENGINE  SPEED. 

The  range  of  governor  action,  so  far  as  the  governor 
itself  is  concerned,  is  obviously  a  constant  amount, 
because  a  certain  amount  of  rise  and  fall  of  the  gover- 
nor balls  will  move  the  cams  a  given  amount.  But  the 
range  of  cut-off  may  be  varied  as  follows:  At  Z  Z'  are 
adjustment  nuts,  by  means  of  which  the  lengths  of  rods 
G  G'  may  be  varied. 

Lengthening  rod  G,  obviously  moves  arm  d  and  its 
cam  n  further  from  the  end  of  latch  link  u,  and  therefore 
prolongs  the  admission  period. 

Shortening  the  rod  G'  causes  cam  n'  to  move  around 
and  away  from  the  leg  g  of  the  latch  link,  and  prolongs 
the  admission. 

The  adjustment  of  the  lengths  of  G  and  G',  may 
therefore  be  employed  for  two  purposes;  first,  to  pro- 
long the  point  of  cut-off,  and  maintain  the  speed  when 
the  engine  is  overloaded,  or  to  hasten  the  point  of  cut- 
off for  a  given  engine  speed,  and  thus  adjust  the  engine 
for  a  lighter  load. 


•.'.-ill 


MOHHItN  .V/V'AU/'   KXGTNKS. 


Fiys.   344  &  345. 


/•///•:  '//.'/•:/-;.v/'/  .1  rro.i/.i  TK:  CUT-OFF  /AW// 


Greene  .  l/t  /on/a  fie  CufcOff  Engine. 


lull  Kngine.    of   which   general    vic\\>   are 

iriven  in    Figs.  344   and    345,    there  are   two  admi- 
uinl  two  exhaust   valves,  each    pair  of  valves  having  its 
own  eccentric,  the  construction  beini:  -'is   follows: 

In  Fig.  :>l'.).  ,J  represents  the  journal-bearing  of  a 
rock  shaft,  having  an  arm  F  connected  to  the  slide- 
spin.  lie  or  valve-rod  G,  and  an  arm  \  at  whose  lower 
extremity  is  the  toe  for  the  trip  motion.  At  J'  is  the 
journal-hearing  for  a  rock  -shaft,  whose  arm  F'  operates 
valve-rod  G',  and  whose  arm  A'  has  ;i  toe  for  the  valve 


•'i:/.  346. 

tripping  mechanism.  The  eccentric  for  the  admission 
valves  operates  the  sliding-bar  C,  in  which  are  the  tap- 
IK-IS  I?  and  1$'.  These  tappets  rest  upon  spiral  springs 
that  are  seated  upon  the  gauge  plate  E,  which  is  raised 
or  lowered  by  the  action  of  the  governor  upon  the  rod 
D. 

The  operation  is  as  follows:  With  the  parts  in  the 
position  shown,  the  sliding-bar  C  is  moving  from  left  to 
right,  as  denoted  by  the  arrow  above  it.  The  toe  B'  is 
operating  arm  A  to  open  the  valve,  whose  rod  or  stem 
is  shown  at  G',  and  will  continue  to  open  it  until  A', 
by  moving  in  the  arc  of  a  circle,  trips  or  escapes  from 
B',  whereupon  the  valve  is  closed  instantly  from  two 
causes,  first,  by  a  weight  attached  to  an  arm  on  the 
rock-shaft  J',  and  secondly,  by  reason  of  the  steam- 
chest  acting  on  an  unbalanced  area  equal  to  the  area  of 
the  valve  stem  C',  the  diameter  of  this  stem  being  en- 


281 


to  the  end  of  obtaining  a  steam  pressure  enough 
to  oven-. une  the  friction  of  the  valve  stem  packing,  and 
also  assist  the  weight  to  move  the  valve  back  quickly, 
and  thus  effect  a  sharp  cut-off.  The  point  at  which  A' 
will  I.e  released  ftom  ]!.  evidently  depends  upon  the 
height  of  1!'  above  the  bar  C,  and  this  is  determined 
by  the  plate  K  and  rod  D,  which  are  actuated  vertically 
by  the  governor. 

By  In-veiling  the  toe  ends  of  arms  A  and  A',  and 
the  upper  faces  of  the  tappets  B'  and  B,  the  arms  are 
enabled  to  pass  over  the  tappets  on  the  return  stroke,  as 
shown  at  A  ]>,  it  being  obvious,  that  toe  A  will  depress 
tappet  B. 

In  this  construction  each  tappet  and  toe  will  always 
come  into  contact,  and  open  the  valve  for  the  admission 
at  the  same  point  in  the  piston-stroke,  hence  the  amount 
of  valve  lead  is  maintained  constant. 

The  exhaust  valves  are  operated  by  a  separate  eccen- 
tric and  shaft,  which  turns  back  and  forth  on  its  axis 
and  operates  the  valves  by  a  positive  motion,  thus  main- 
taining the  points  of  release  and  of  compression  con- 
stant. 

The  Harris  Corliss  Engine 

Fig.  347  is  a  back  view  of  the  Harris  Corliss  Engine, 
in  which  glands  for  the  valve  stems  are  dispensed  with 
by  the,  construction  shown  in  Fig.  348,  in  which  A  re- 
presents the  valve,  and  a,  a  thrust  collar  whose  diameter 
is  made  larger  than  that  of  the  valve  stem,  so  as  to  pre- 
sent an  area  large  enough  to  receive  an  unbalanced 
steam  pressure  at  the  other  end  of  the  valve  that  will 
keep  the  valve  seated  endways  against  the  thrust-collar 
and  maintain  a  steam-tight  joint  without  the  use  of 
shifting  boxes. 

TJie  Fishkill  Engine. 

In  Fig.  349  is  shown  the  Fishkill  Engine,  which  is  of 
the  Corliss  type.  In  the  smaller  sizes  of  these  engines 
an  ordinary  dash-pot  is  employed,  but  in  the  larger 
sizes  a  vacuum  under  the  plunger  is  employed  to  assist 
in  closing  the  valve  after  it  is  released.  The  valves  are 
held  to  their  seats  by  spiral  springs,  so  that  they  may 
follow  up  the  wear,  and  thus  prevent  leakage. 


232 


MOUEltX  STEAM  ESU 


rut: 


231 


23-1  MODERN  WE  AM  ENGINES. 

The  W7welock  Automatic  Cid~Off  Engine 


The  general  construction  of  the  Wheelock  Engine 
is  seen  in  Fig.  350,  which  is  a  back  view  showing  the 
valve  gear,  which  is  more  fully  shown  in  Fig.  351. 
The  parts  are  shown  in  the  positions  they  occupy  at  the 
point  of  cut-ofl  at  half-stroke,  the  piston  moving  from 


PJISS  through  and  form  guide   pins  for  the  square  latch 
blocks  which  are    shown  in  dotted  lines. 

The  latch  blocks  are  attached  respectively  to  the  ad- 
mission links  D  and  D',  by  cylindrical  stems  seated  in 
the  admission  links,  which  are  fast  upon  the  stems  V  V 
of  the  admission  valves.  The  lower  arm  of  each  ad- 
mission link  is  pivoted  to  the  top  of  the  weight  ~\V  of 


Fig.  350. 

The  Wheelock  Automatic  Cut-Off  Engine. 


the  head-end    to  the    crank-end    of  the  cylinder. 

At  E  and  E'  are  the  stems  of  the  exhaust  valves  to 
which  are  fixed  the  links  F  and  F',  which  are  connected 
together  by  the  rod  G. 

Hence  the  rod  Z  from  the  eccentric  operates  both  ex- 
haust valves  by  a  direct  and  positive  motion.  At  h 
and  h'  are  nuts  for  adjusting  the  length  of  rod  G. 

The  latch  links  L  and  L'  are  pivoted  to  the  exhaust 
links  L  L',  at  m  and  ra',  as  are  also  the  tongues  which 


the  dash-pot,  the  pivots  being  shown  by  dotted  circles 
p  //.  The  rod  from  the  governor  attaches  at  f,  to  the 
arm  of  the  trip  piece  or  trip  cam  e,  while  the  rod  R  H 
connects  arm/'  with/  I'pon  /'  is  a  pinion  engaging 
with  teeth  upon  the  trip  cam  or  trip  <•',  which  is  free  to 
revolve  upon  V.  The  latch  link  L'  has,  by  contact 
with  the  trip  cam  at  point  r,  been  lifted,  thus  throwing 
the  end  of  the  steel  strip  «  (with  which  the  latch  link 
is  faced)  out  of  contact  with  the  latch  block,  hence 


THE  \VIir.KLOCK  AUTOMATIC  CUT-OFF  EXG1SE. 


230 


30 


136 


MODERN  STEAM  EN  GINKS. 


the  weight  W  of  the  dash-pot  is  at  liberty  to  fall  and 
operate  the  valve  stem  V,  arid   thus  effect  the  cut-off. 
The  weight  is  assisted  by  a  spiral  spring  Q,  hence  it 
closes  the  valve  quickly. 


THE    CONSTRUCTION    OF     THE    DASH-POT. 

The  weights  "W  are  air-cushioned  by  the  following 
means:  A  sectional  view  taken  through  the  center  of 
the  dash-pot  on  a  plane  at  a  right  angle  to  the  cylinder, 
is  shown  in  Fig.  352.  The  base  A  is  pivoted  on  the 


Fig.   352. 

supporting  stem  B,  a  washer  W,  secured  by  a  set  screw 
«,  preventing  end  motion,  while  leaving  the  dash-pot 
free  to  vibrate  upon  B  as  a  pivot.  Fixed  in  the  base  A 
is  the  pin  P,  which  acts  as  a  guide  to  the  weight  "W. 
At  Y  Y,  the  base  fits  into  the  recess  c,  shown  in  the 
bottom  of  the  weight  W.  Suppose  then,  that  the  latch- 
block  of  the  valve  gear  has  been  released,  and  that  the 
weight  W  has  fallen  to  the  position  it  occupies  in  Fig. 
351,  and  has  therefore  closed  the  valve  and  effected  the 


cut-off,  and  the  recess  c  will  be  filled  with  enclosed  air, 
which  acts  as  a  cushion  because  it  cannot  escape  freely 
past  the  section  Y  Y,  of  the  base,  and  is  therefore 
momentarily  compressed,  allowing  the  weight  to  seat 
quietly  down  to  the  leather  valve  V  V.  The  function 
of  this  valve  is  as  follows:  Suppose  the  weight  to  be 
seated  down  as  it  is  at  W.  in  Fig.  351,  and  lifting  it 
quickly  for  the  next  admission  would  cause  a  partial 
vacuum  in  the  recess,  c  and  thus  increase  the  duty  of 
lifting  the  weight  "W,  and  opening  the  admission  valve. 

This  however,  is  obviated  by  the  leather  valve  v  v. 
which  covers  air  holes  H  h,  this  valve  lifting  when  W 
is  raised,  and  admitting  air  into  recess  c. 

To  regulate  the  quantity  of  air  thus  admitted,  a 
screw  S  is  provided,  its  head  fitting  the  bore  b,  and  it  is 
obvious  that  it  may  be  screwed  to  the  left  and  caused 
to  close  communication  between  the  air  holes  H  h,  or 
to  the  right,  leaving  a  more  free  communication  between 
them. 

By  pivoting  the  latch  links  upon  the  eccentric  pins 
m  m'  in  Fig.  351,  a  certain  amount  of  adjustment  is 
obtained.  Considering,  for  example,  latch  link  L  in 
Fig.  351,  and  revolving  its  eccentric  pivot  m  to  the 
right  will  act  to  shorten  the  latch  link  with  relation  to 
the  valve  stems  E  V,  and  this  would  cause  the  latch 
block  to  engage  earlier  in  the  stroke,  and  thei'efore 
hasten  the  admission  and  increase  the  valve  lead.  Or 
turning  m  to  the  left,  would  have  the  opposite  effect. 

Furthermore,  shortening  the  latch  links  by  means  of 
these  eccentric  pivots,  causes  the  weights  W  and  W  to 
lift  higher,  and  this  by  increasing  the  tension  of  the 
spring  Q  Q,  has  the  same  effect  as  increasing  the 
weights  W  W. 

THE    COMPRESSION. 

The  amount  of  compression  is  regulated  by  altering 
the  lengths  of  the  rods  Z  and  G,  the  former  having  an 
adjustment  nut  (not  shown  in  fig.  351)  and  the  latter 
having  adjustment  nuts  h  and  h'. 

EQUALIZING    THE    POINTS    OF    CUT-OFF. 

The  points  of  cut-off  may  be  equalized  as  follows: 
Suppose  the  adjustment  nut  n'  is  operated  to  lengthen 
rod  R,  and  arm  /'  will  be  moved  to  the  left.  This  will 


TUK  \V1U-:EL<X'1\  M'TuMATir  CUT-OFF  ENGINE. 


237 


move  the  trip  cam,  BO  as  to  bring  its  tripping  point  r 
more  nearly  vertical,  and  hasten  the  point  of  cut-oil. 
or  vice  versa,  'employing  nut  »'  to  shorten  rod  H,  will 
move  point  r  to  the  left,  ami  delay  tin-  point  of  cut-off. 

Similarly  for  the  crank-end  valve,  whose  stein  is 
shown  at  V,  operating  adjustment  nut  »  to  move  K,  and 
therefore/  to  the  right,  will  cause  the  latch  link  to  meet 
the  trip  cam  at  s  quicker,  and  hasten  the  cut-off,  while 
employing  H  to  move  K  (and  therefore/)  to  tbe  right. 
will  cause  contact  at  s  to  be  delayed,  and  prolong  the 
point  of  cut-off  for  valve  V 

The  two  links  F  and  F'  have,  from  their  peculiar 
shape,  a  motion  corresponding  to  the  wrist  motion  of 
the  Corliss  Engine,  opening  the  valves  quickly  during 
admission,  and  slowly  while  the  lap  of  valve  is  passing 
over  the  port,  thus  the  position  of  F  is  such  that  its 
motion  transmits  a  very  slight  degree  of  motion  to  the 
latch  link  L,  while  F'  is  in  position  to  move  its  latch 
link  L'  quickly. 

In  the  later  forms  of  this  engine  a  flat  griddle  or 
multiported  valve  and  valve  seat  is  employed,  the  stems 
K  and  E'  moving  the  valve  by  a  short  link  that  also 
has  tiie  effect  of  a  wrist  motion  in  retarding  the  valve 
movement  during  that  part  of  the  stroke  when  the 
cut-off  is  to  be  effected.  The  latch  blocks  seat  against 
a  piece  of  leather,  and  being  narrower  than  the  latch 
notch  have,  after  passing  it,  a  slight  motion  along  it. 
Thus  while  the  latch  link  L  is  moving  downwards,  as 
denoted  by  its  arrow,  the  latch  will  remain  stationary 
while  the  tongue  slides  through  it.  On  account  of  the 
position  of  the  point  of  suspension  m  of  the  latch 
link,  F  can  have  considerable  motion  without  alter- 
ing the  position  of  the  latch  block  upon  the  leather. 


The  Twiss  Engine. 

Fig.  353  represents  an  Automatic   Cut-Off    Engine, 
constructed  by  N.  W.  Twiss.     The  cut-off  eccentric-rod 


is  here  pivoted  to  the  upper  end  of  a  link,  that  is  piv- 
oted at  its  lower  end,  and  therefore  vibrates  in  an  arc 
of  constant  length.  The  link-block  is  attached  to  the 
rod  for  ojx>rating  the  cut-off  valves,  and  the  governor  is 
attached  to  this  same  rod.  It  is  obvious,  that  according 
as  the  governor  moves  the  rod,  and  therefore  the 
link-block  down,  the  travel  of  the  cut-off  valve  is  re. 
duceil.  and  the  point  of  cut-off  hastened,  until  upon  the 
center  of  the  link-block,  becoming  in  line  with  the  cen- 
ter of  oscillation  of  the  link,  the  cut-off  valve  would 
remain  motionless,  and  their  would  be  no  admission. 
The  steam  chest  is  pierced  at  each  end  directly  under- 
neath the  bore  of  the  cylinder,  for  the  reception  of  four 
circular  slide  valves,  one  main  valve,  and  one  cut-off 
valve  at  each  end  of  the  cylinder,  thus  securing  the 
least  possible  amount  of  clearance.  Steam  is  admitted 
and  exhausted  by  the  main  valves.  The  cut-off  valves 
are  located  inside  of  the  main  valves  and  concentric 
herewith,  they  are  made  double  opening  by  means  of 
a  cavity  in  their  centers,  thus  reducing  the  amount  of 
travel  nearly  one-half.  These  valves  have  the  prsssure 
of  steam  upon  them  and  are  made  to  compensate  for 
wear  upon  their  seats.  The  main  valves  receive  their 
motion  by  means  of  drivers,  having  hollow  .stems  pass- 
ing through  long  bonnets  secured  to  the  steam  chest;  to 
these  steins  cranks  are  keyed.  These  cranks  are  con- 
nected together  by  a  pitman  which  receives  its  motion 
from  an  eccentric  on  the  main  shaft,  the  eccentric-rod 
is  made  to  disengage  on  the  larger  sizes  by  which 
means  the  engine  may  be  worked  backward  or  forward 
at  the  will  of  the  engineer.  The  cut-off  valves  receive 
their  motion  by  means  of  stems  which  pass  through  the 
hollow  stems  of  the  main  valve  drivers,  at  the  extremi- 
ties of  which  cranks  are  keyed.  These  cranks  are  also 
connected  together  by  a  rod,  and  receive  their  motion 
from  another  eccentric  on  the  main  shaft.  The  range 
of  cut-off  being  from  zero  to  five-eighths  stroke,  and 
the  speed  of  the  engine  may  be  changed  while  the  en- 
gine is  running,  by  adding  or  removing  weights  from 
the  governor. 


'.>3S 


MODERN  STEAM  ENGINES. 


V 


•5*          M 

r** 

^ 


CHAPTER    VTIL 


THE 


EXSINE. 


In  a  Compound  Engine  there  are  two  or  more  cylin- 
ders, each  partly  utilizing  the  steam.  The  first,  which 
recieves  steam  from  the  boiler,  is  the  high  pressure 
cylinder,  in  which  the  steam  performs  a  certain  amount 
of  duty  before  being  exhausted  into  a  receiver,  or  into 
t'ne  steam  pipe  of  the  low  pressure  cylinder,  as  the  case 
may  be.  The  receiver  is  a  chamber  from  which  the 
second  cylinder  receives  its  supply  of  steam. 

The  live  steam  period,  in  a  compound  engine,  is  con- 
fined to  the  period  of  admission  of  the  H.  P.  (or  high 
pressure)  cylinder,  since  after  the  point  of  cut-off  in 
the  H.  P.  cylinder,  the  steam  performs  work  from  its 
expansion  only. 

The  object  of  compounding  is  to  enable  the  use  of  a 
higher  pressure  of  steam  without  increasing  the  pres- 
sure of  the  exhaust,  or,  in  other  words,  to  enable  the 
steam  to  be  used  more  expansively,  and,  in  some  cases, 
to  enable  the  piston  power  to  be  transmitted  to  the 
crank  with,  greater  uniformity. 

Furthermore,  by  dividing  up  the  expansion  between 
two  cylinders,  there  is  less  variation  in  the  temperature 
of  the  cylinder  at  the  beginning  and  end  of  the  stroke, 


and,  therefore,  less  condensation  during  the  admission 
period.  As  the  exhaust  steam  from  the  H.  P.  cylinder 
is  that  which  drives  the  L.  P.  piston,  it  follows  that 
there  is,  on  the  exhaust  side  of  the  11.  P.  piston,  a  back 
pressure  that  is  theoretically  equal  to  the  pressure  of 
steam  admitted  to  the  L.  P.  cylinder.  In  practice, 
however,  there  is  found  to  be  a  loss  of  two  or  three  Ibs. 
per  square  inch,  while  the  steam  passes  from  the  H.  P. 
cylinder,  and  through  the  reciever  to  the  L.  P.  cylinder. 

There  are  two  principal  methods  of  compounding. 
In  the  first  the  exhaust  from  the  high  pressure  cylinder 
passes  through  a  pipe  leading  direct  to  the  steam  chest 
of  the  L.  P.  cylinder.  In  the  second  the  H.  P.  exhaust 
passes  into  a  reciever  or  chamber,  intermediate  between 
the  two  cylinders. 

When  a  second  L.  P.  cylinder  is  employed  the  engine 
is  termed  a  triple  expansion  engine. 

In  stationary  engines  the  prevailing  method  of  com- 
pounding is  to  place  the  low  pressure  cylinder  in  line 
with  the  high  pressure,  both  pistons  l>eing  on  one  rod. 
This  method  is  also  employed  upon  some  of  the  smaller 

sizes  of  marine  engines,  as  those  used  for  vachts.      Fig. 

-'39 


240 


MODERN  STEAM  ENGINES. 


354  is  an  example  of  this  arrangement,  H.  P.  is  the  high 
pressure  cylinder,  the  exhaust  steam  passing  from  the 
exhaust  side  E  of  the  piston  through  the  pipe  P  into 
the  steam  chest  C  of  the  low  pressure  cylinder. 
Direct  passage  of  the  exhaust  steam  from  one  cylinder 
to  the  other  without  passing  into  a  reciever  is  only  per- 
missible when  the  two  pistons  are  on  one  rod,  as  in  the 
figure,  or  else  when  each  piston  connects  to  its  own 


Fig.  354. 

crank  and  the  two  cranks  are  opposite  to  each  other  so 
that  the  pistons  will  reach  opposite  ends  of  the  stroke 
simultaneously,  and  the  low  pressure  piston  will  be 
in  position  to  recieve  steam  at  the  same  time  that  the 
high  pressure  cylinder  begins  to  exhaust. 

Thus  in  the  figure  the  L.  P.  piston  is  in  position 
to  recieve  the  exhaust  from  the  H.  P.  cylinder,  both 
pistons  being  at  the  ends  of  their  strokes.  Obviously, 


however,  if  the  two  cylinders  were  independently  con- 
nected to  the  crank  (each  having  its  own  piston-rod  and 
connecting-rod)  the  L.  P.  piston  might  be  at  the  other 
end  of  the  cylinder,  and  still  be  in  position  to  recieve 
the  exhaust  steam  from  E,  because  both  pistons  would 
still  begin  and  end  their  strokes  together,  the  point 
of  release  of  the  H.  P.  corresponding  to  the  point  of 
admission  of  the  L.  P.  cylinder. 

In  the  engines  of  ocean  steamships,  the  H.  P.  and  L. 
P.  cylinders  are  separately  connected  to  the  crank,  whose 
throws  are  at  a  right  angle  one  to  the  other,  so  that 
when,  as  in  Fig.  355,  the  H.  P.  piston  is  at  the  end  of  its 
stroke  and  its  exhaust  opens,  the  L.  P.  piston  is  near  the 
middle  of  the  cylinder.  These  relative  positions  ren- 
der a  receiver  necessary,  so  that  a  supply  of  steam  may 
be  at  hand  for  the  L.  P.  piston  at  the  commencement  of 
its  stroke.  "When  the  high  and  low  pressure  pistons 
are  upon  the  same  rod  as  in  Fig.  354,  the  back  pressure 


HP 


LP 


Fiij.   355. 

on  the  H.  P.  piston  fluctuates  more  than  it  does  when 
they  are  independent,  and  the  cranks  are  at  a  right 
angle.  Thus,  suppose  the  high  pressure  piston  to  be  at 
the  end  of  its  stroke,  as  in  Fig.  354,  and  the  back  pres- 
sure will  be  at  its  greatest,  because  the  exhaust  lias  just 
begun.  Its  reduction  will,  however,  proceed  regularly 
with  relation  to  the  piston  motion,  because  both  pistons 
travel  in  unison  throughout  every  point  in  the  stroke. 
But  suppose  the  cranks  are  at  a  right  angle,  and  when 
the  H.  P.  piston  is  at  the  end  of  its  stroke,  as  in  Fig. 
355,  and  the  exhaust  opens,  we  have  the  following 
conditions: 

First,  the  exhaust  steam  from  the  H.  P.  cylinder  will 
perform  a  certain  amount  of  expansion  in  the  receiver, 
which  will  reduce  its  pressure,  and  secondly,  the  L.  P. 
piston  is  in  that  part  of  its  stroke  during  which  it  moves 
the  fastest,  and  is  therefore  drawing  most  rapidly  upon 
the  steam  in  the  receiver,  while  the  H,  P,  piston  is  in 


FARCUT's  r 


l-;.\  (,  L\  I-;. 


241 


that  part  of  its  stroke  during  which  it  moves  tlie  slow- 
est,  hence  the  relative  speeds  of  the  two  pistons  (as  well 
as  the  receiver),  acts  to  diminish  tin-  pressure  during  tin- 
early  part  of  ouch  low  pressure  piston  stroke,  and  this 
obviously  acts  to  equalize  the  receiver  and  L.  1'.  cylin- 
der pressure  throughout  the  stroke.  The  amount  of 
power  developed  by  the  engine,  however,  is  not  influ- 
enced by  the  fluctuation  of  back  pressure  in  the  high 
pressure  cylinder,  or  of  the  pressure  during  the  admis- 
sion period  of  the  low  pressure  cylinder,  but  is  deter- 
mined by  the  diameter  of  the  high  pressure  cylinder, 
the  pressure  of  the  live  steam,  the  point  of  cut-off  for 
the  high  pressure  piston,  and  the  number  of  times  the 
steam  is  expanded  in  the  low  pressure  cylinder,  or,  in 
other  words,  the  power  developed  is  determined  by  the 
volume  and  total  pressure  (pressure  above  a  perfect 
vacuum)  of  the  live  steam  and  the  unbalanced  pressure 
on  the  low  pressure  cylinder  at  the  point  of  low  pressure 
exhaust.  In  average  practice,  the  diameter  of  the  high 
pressure  cylinder  is  twice  that  of  the  low  pressure,  and 
the  points  of  cut-off  are  at  about  J  stroke  for  the  high 
pressure,  and  at  about  £  stroke  for  the  low  pressure 
cylinder,  these  proportions  being  chosen  so  as  to  have 
the  jiower  about  equally  divided  between  the  two  pis- 
tons. 

To  find  the  total  range  of  expansion,  (which  is  not 
affected  by  the  method  of  compounding),  we  divide  the 
capacity  of  the  low  pressure  cylinder,  including  the 
contents  of  one  steam-port  and  steam  passage,  by  the 
space  moved  through  by  the  high  pressure  piston,  up  to 
the  point  of  cut-off  including  the  space  in  one  steam- 
port  and  passage,  and  the  quotient  is  the  ratio  of  ex. 
pansion,  this  is  clear,  because  we  have  merely  found 
how  many  times  the  total  space  occupied  by  the  live 
steam  has  been  increased.  The  amount  of  power  de- 
veloped by  the  engine  may  be  varied  by  altering  the 
point  of  cut-off  for  either  the  high  or  the  low  pressure 
cylinder,  or  for  both. 

When  the  cranks  are  at  a  right  angle,  and  a  receiver  is 
used,  it  is  usual  to  vary  the  power,  by  altering  the  point 
of  cut-off  for  the  high  pressure  cylinder  only.  But 
when  both  pistons  are  on  one  rod  the  two  valves  may 
be  on  one  rod,  and  the  valves  being  given  equal  lap 
and  travel,  the  points  of  cut-off  correspond  in  the  two 
cylinders,  and  will  be  altered  alike  and  simultaneously 


In  Fig.  35-1.  as  the  two  pistons  are  on  one  rod,  and 
therefore  at  corresponding  pnmis  in  the  stroke,  tin-  fol- 
lowing arrangement  is  permitted.  The  low  pressure 
cylinder  has  a  single  valve  V,  and  on  the  same  stem  is 
a  main  valve  r  for  the  high  pressure  cylinder,  which  is 
provided  with  a  cut-off  valve  v',  each  valve  being  shown 
placed  in  mid  position.  As  the  two  valves  V  v  are  on  the 
same  rod.  and  therefore  have  equal  amounts  of  travel, 
their  amounts  of  steam  lap  must  be  equal,  if  both  valves 
are  to  have  equal  lead,  and  the  points  of  cut-off  will,  if 
effected  by  these  valves,  be  at  corresponding  but  fixed 
points  in  the  stroke.  By  means  of  the  cut-off  valve, 
however,  the  point  of  cut-off  of  the  high  pressure  cylin- 
der may  be  varied,  thus  varying  the  admission  period 
and  the  amount  of  expansion,  and  therefore  the  power 
of  the  engine.  In  order  to  proportion  the  amount  of 
steam -port  opening  to  the  diameters  of  the  cylinders, 
the  high  pressure  cylinder  and  valve  is  single  ported, 
while  the  low  pressure  cylinder  has  a  double  ported 
valve  and  steam-port 


Farcotfs  Compound  Engine. 

Fig.  356  represents  Farcot's  Single- Acting  Compound 
Engine,  in  which  one  valve  serves  for  both  cylinders. 
The  high  pressure  piston  receives  steam  on  its  upward 
stroke  only,  and  the  low  pressure  piston  on  its  down- 
ward stroke  only,  and  as  there  is  no  steam  pressure 
between  the  two  pistons,  therefore  there  is  no  back 
pressure  on  the  high  pressure  piston. 

The  live  steam  pipe  enters  at  the  end  n  of  the  valve, 
and  therefore  acts  to  counter-balance  the  weight  of  the 
valve,  etc.  The  pistons  are  shown  at,  the  end  of  the 
downward  stroke,  the  live  steam -port  being  open  to  the 
amount  of  the  lead.  The  low  pressure  cylinder  is  open 
to  the  exhaust  which  passes  through  the  jort  in  the 
valve,  and  finds  exit  at  C.  The  valve  action  may  be 
understood  from  figs.  357,  358,  359,  360,  and  301. 

In  fig.  357  the  valve  v  is  shown  in  the  position  it 
would  occupy  with  the  crank  on  the  lower  dead  center, 
and  therefore  corresponding  to  the  position  of  the 
parts  in  fig.  356  the  valve  being  supposed  to  have  no 
lead.  A,  represents  the  port  for  the  high  pressure,  and 


•242 


MODERN  STEAM  ENGINES. 


V  that  for  the  low  pressure  cylinder,  d  is  an  exhaust 
port  for  the  low  pressure  cylinder,  while  C  corresponds 
to  the  exit  C  in  the  vertical  section,  fig.  356. 

In  fig.  358  the  valve  is  shown  at  the  end  of  its  stroke, 
the  high  pressure  cylinder  port  a,   being  full  open,  and 


close  the  low  pressure  exhaust  at  C,  this  being  the  edge 
that  effects  the  compression  for  the  L.  P.  cylinder. 

Continuing  the  motion,  when  the  edge  /  of  the  valve 
reaches  the  edge  a  of  the  high  pressure  port,  as  in  fig. 
359  the  high  pressure  exhaust,  and,  therefore,  the  low 


the  exhaust  from  the  low-  pressure  cylinder  passing  from 
J  through  d  to  C.  Fig.  357  also  shows  the  valve  at  the 
point  of  cut-off  for  the  high  pressure  cylinder,  and  it 
is  seen  that  the  admission,  the  cut-off  and  the  compres- 
sion is  effected  by  the  end  e  of  the  valve,  and  that  after 
the  cut-off  is  effected,  the  edge  g  of  the  valve  begins  to 


356. 


pressure,  admission  begins,the  exhaust  at  C,  being  closed 
by  the  edge  g  of  the  valve.  Fig.  360  shows  the  valve  at 
the  end  of  its  stroke,  port  a  being  full  open,  and  the 
opening  at  I  equal  to  that  at  a.  From  the  position  in 
fig.  360  the  valve  moves  to  that  shown  in  fig.  357.  and 
we  have  now  followed  the  motion  throughout  a  full 


x  COMPOUND  /•/.Y'.Y.Y/;. 


243 


revolution  of  the  engine.  It  will  he  M-en  that,  tin- 
ports  a  and  b  correspond  to  tin-  ordinarv  steam  and 
exhaust  ports  of  a  common  slide-valve  engine,  ami  the 


/•'</.   357. 

dimension  c/  fig.  357,  of  the  valve,  corresponds  to  the  lip 
of  an  ordinary  slide-valve,  while  the  port  d  corresponds 
to  the  exhaust  cavity  of  a  slide-valve,  and  all  these  parts 
may  be  proportioned  by  the  means  already  described 
31 


with  reference  to  diagrams  for  designing  valve  motions, 
all  that  remains,  therefore,  is  to  determine  the  position 
of  the  port,  ( ',  which  must  l>e  so  located  that  when  the 


NT 

Fig.  360. 

high  pressur^  exhaust  occurs,  and  the  valve  is  in  the 
position  shown  in  fig.  359  the  edge  g  of  the  valve, 
must  lap  over  port  C  sufficiently  to  maintain  a  steam 
tight  joint 


(UNIVERSITYJ 

V      «      °T 

^^CALirORN-*-. 


CHAPTER  IX. 


THE  CONDENSING  EXGIXE. 


A  steam  engine  is  termed  a  condensing  engine  when 
it  is  provided  with  a  condensing  apparatus,  in  which  the 
exhaust  steam  is  condensed  by  water,  instead  of  pas 
sing  directly  into  the  atmosphere. 

The  object  of  employing  a  condenser,  is  to  form  a 
vacuum  on  the  exhaust  side  of  the  piston  engine,  and 
thus  remove  from  it  the  resistance  of  the  atmosphere, 
amounting  to  an  average  of  about  14T^  pounds  per 
square  inch.  The  effective  power  of  the  live  steam,  and 
therefore  that  of  the  engine,  is  thus  increased  to  an 
amount  answering  to  the  degree  of  perfection  of  the 
vacuum. 

Condensers  may  be  classified  under  two  general 
heads,  viz. ;  jet  and  surface  condensers,  this  distinction 
arising  from  their  construction,  and  the  manner  in 
which  the  condensing  water  is  used.  In  the  ordinary 
jet  condenser,  the  water  is  (by  passing  through  many 
small  openings)  divided  into  sprays,  which  condense 
the  steam  by  direct  contact,  the  condensed  steam  and 
condensing  water  being  then  discharged  by  an  air 
pump.  This  air  pump  also  discharges  the  air  which  is 
liberated  from  the  water  in  the  boiler  during  the  pro- 
cess of  evaporation  (and  separated  from  the  steam  by 

the  process  of  condensation),  and  that  which  may  enter 
244 


from  leaks  in  the  joints  of  the  engine,  or  in  the  pipes, 
or  from  a  leak  in  the  stuffing-box  of  the  engine  piston, 
together  with  any  other  uncondensible  gases  which  may 
be  present. 

In  the  Ejector  Condenser,  the  condensing  water  is  in- 
troduced through  a  nozzle  in  a  solid  jet,  and  is  ejected 
against  the  pressure  of  the  atmosphere  by  the  combin- 
ed action  of  the  exhaust  steam,  and  a  natural  or  artifi- 
cial head  or  pressure  of  water,  thus  enabling  an  air 
pump  to  be  dispensed  with. 

The  Siphon  Condenser  also  operates  without  the  aid 
of  an  air  pump,  provided  that  the  condensing  water 
can  be  had  at  an  elevation  of  not  less  than  1 0  feet,  the 
exhaust  pipe  of  the  engine  being  extended  to  a  height 
of  34  (or  more)  feet  above  the  hot-well.  The  conden- 
ser is  attached  to  the  top  of  the  exhaust  pipe,  while  one 
or  more  vertical  air-tight  discharge  pipes  connect  the 
condenser  to  the  hot-well  below.  The  air  in  the  con- 
denser and  pipes  is  first  expelled  by  the  exhaust  steam, 
and  the  water  injected  into  the  condenser  forms  a  par- 
tial vacuum.  The  condensed  steam  and  condensing 
water  pass  down  to  the  hot- well,  because  the  column  in 
the  discharge  pipe  is  higher  than  can  be  sustained  by 
the  pressure  of  the  atmosphere.  The  air  and  gases  are. 


7V/ A'  CONDENSING   i-:.\<iL\i-:. 


245 


more  or  less,  perfectly  exhausted  by  the  column  of 
water  falling  through  the  discharge  pipe,  thus  maintain- 
ing the  vacuum.  Unless,  however,  a  head  of  20  feet 

can  be  had  for  the  condensing  water,  the  vacuum  must 
:irst  formed  or  started,  cither  by  a  pump  or  its  equiv- 
alent, or  by  the  special  arrangement  of  pipes,  which 
will  he  described  hereafter  with  reference  to  the  Bulk. 
ley  Injector  condenser. 

In  a  surface  condenser,  the  exhaust  steam  is  conden- 
sed by  metallic  surfaces,  in  the  form  of  tubes,  cylinders, 
or  plates,  which  are  kept  cool  by  a  circulation  of  water. 
Ordinarily  thin  brass  tubes  are  employed,  the  conden 
sing  water  being  circulated  through  them  by  a  pump,  the 
-team  is  condensed  on  the  external  surface  of  the  tubes, 
and  falls  into  the  condenser,  from  which  it  is  discharged 
by  the  air-pump.  Thus  the  condensing  water  and  the 
water  of  condensation  are  kept  entirely  separate  and 
the  latter  may  be  returned  to  the  boiler,  while  the  con 
densing  water,  which  may  be  salt  or  otherwise  impure, 
pa-ses  away.  Ocean  steamships,  and  other  vessels  ply- 
ing on  salt  water,  are  provided  with  surface  condensers, 
as  are  also  some  land  engines,  when  it  is  not  desirable 
to  use  the  conden-ing  water  in  the  boilers,  or  where  a 
proper  quantity  of  water  for  boiler  use  is  scarce.  A 
surface  condense]-  require.*  therefore,  a  circulating  as 
well  as  an  air-pump. 

Tlie  Bulkley  Injector  Condenser. 

Bulkley 's  Injector  Condenser  is  arranged  on  the  siph- 
on principle,  but  has,  in  place  of  the  ordinary  conden- 
ser, an  injector  containing  an  exhaust  nozzle,  shown  at  C 
in  Fig.  ;{G1.  The  condensing  water  enters  around  this 
nozzle,  and  passes  down  into  the  condenser  through  a 
narrow  annular  orifice.  The  exhaust  steam  entering 
this  film  of  water,  is  instantly  condensed,  and  imparts 
its  power  to  the  injection  water  in  a  direct  line  down 
the  discharge  pipe.  The  speed  of  the  water  through 
the  contracted  neck  of  the  condenser  (which  it  com- 
pletely fills)  enables  it  to  draw  out  the  air  and  un- 
condensible  vapor,  into  the  enlarged  discharge  pipe 
below. 

The  general  arrangement  of  the  condenser  and  its 
pipes  is  shown  in  Fig.  362.  The  exhaust  pipe  of  the  en- 


gine is  carried  up  to  a  height  of  about  .'!4  feet  above 
the  hot-well,  which  should  be  placed  at  the  lowest  point 
convenient  for  draining  it.  A  feed  water  heater,  if  air- 
tight, may  be  set  in  the  exhaust  pipe  between  the  en- 
gine and  condenser  If  the  condenser  has  a  natural 
head  of  not  more  than  10  feet  (or  what  is  the  same 
thing,  a  pressure  of  about  4A  Ibs.  per  square  inch),  the 
condenser  requires  the  service  of  a  pump  merely  to 
start  it,  because  after  the  vacuum  is  once  started 
the  atmospheric  pressure  will  cause  the  condensing  water 
to  flow  into  the  condenser,  thus  dispensing  with  the  em- 
ployment of  either  an  air  or  water  pump.  If  the  con 
densing  water  has  a  head  of  20  feet  (corresponding  to 
a  pressure  of  nearly  9  Ibs.  per  square  inch),  the  conden- 
ser may  be  so  constructed  as  to  start  itself  independent 
of  any  pump,  and  an  example  of  this  arrangement  will 
be  given  presently.  This  obviously  saves  the  power  re- 
quired to  operate  an  air  pump.  In  cases  when  a  less 
head  of  water  exists  and  the  service  of  a  pump  is  re- 
quired continuously,  the  pump  has  but  little  duty  to 
perform,  because  the  vacuum  will  permit  the  atmos- 
pheric pressure  to  raise  the  condensing  water  about  2o 
out  of  the  34  feet.  Furthermore,  the  exhaust  steam 
from  the  pump  may  enter  the  condenser  giving  the 
pump  piston  the  benefit  of  the  vacuum,  hence  the  con. 
sumption  of  steam  by  the  pump  wil'  be  reduced  to  its 
lowest  limits  The  vertical  discharge  pipe  from  the 
condenser  passes  below  the  surface  of  the  water  .11  the 
hot- well,  and  is  therefore  sealed  by  the  water  in  the 
same,  hence  the  condenser  and  the  discharge  pipe  form 
a  barometric  column  about  34  feet  high,  and  the  water 
falls  from  tl  e  condenser  to  the  hot-well,  because  even  a 
perfect  vacuum  in  the  exhaust  pipe  wou'd  l>e  insufficient 
to  sustain  a 'column  of  water  of  that  height.  The  con- 
struction therefore  effects  a  virtually  positive  action  in 
extracting  the  air  and  uncondensible  gases  from  the  con- 
denser, nor  can  the  condensing  water  pass  over  into  the 
cylinder  of  the  engine,  because  the  water  is  directed 
downwards,  and  the  area  of  the  contracted  throat  of 
the  condenser  is  greater  than  that  of  the  annular  inlet 
opening,  afforded  by  the  nozzle  C,  in  Fig.  361. 

A  relief  valve  is  placed  on  top  of  the  exhaust  pipe, 
so  that  the  engine  may  work  without  the  condenser,  if 
the  vacuum  is  lost  from  any  cause.  It  opens  automat- 
ically, and  is  closed  air-tight  by  atmospheric  pressure  as 


246 


MODERN  STEAM  EX  (JIM US. 


361.    Eulkley's  Siphon  Condenser. 


;  /•: \ i ,' / \ /•:. 


247 


Application  of  Bulkley's  Injector  Condenser. 


248 


MODKUN  STEAM  ENGINES. 


soon  as  the  vacuum  is  formed.  As  before  stated,  this 
condenser  will  siphon  over  the  water,  from  a  head  of  9 
or  10  feet  after  starting,  but  the  vacuum  must  first  be 
formed  by  drawing  out  the  air  by  an  ejector,  or  elevat- 
ing the  water  by  a  pump,  to  the  condenser.  With  a  natu- 
ral head  of  19  or  20  feet,  the  condenser  may  be  started 
by  the  use  of  a  valve  connecting  the  vertical  discharge 
and  injection  pipes,  just  below  the  water  level.  This  is 
shown  in  Fig.  363.  The  natural  level  of  the  water,  is 
shown  in  the  flume,  or  source  of  supply,  at  about  20 
feet  above  the  level  of  the  water  at  the  over  flow  of 
the  hot-well.  Now,  by  expelling  the  air  from  the  en- 
gine and  pipes  by  exhaust  steam,  and  opening  the  con- 
necting valve  V,  the  water  will  flow  over  from  the 
flume,  and  down  the  vertical  discharge  pipe,  condensing 
the  steam,  and  thus  form  a  partial  vacuum.  The 
water  in  the  supply  pipe  will  then  be  forced  up  to  the 
condenser,  by  the  atmospheric  pressure,  thus  perfecting 
and  maintaining  the  vacuum.  The  valve  V  is  closed  as 
Boon  as  the  vacuum  is  formed. 

There  is  required  for  condensation,  an  amount  of 
water  equal  to  from  20,  to  25  times  the  weight  of  the 
exhaust  steam,  and  as  the  condensing  water  lias  a  tem- 
perature of  about  100  degrees  in  the  hot-well,  it  may 
be  used  for  feeding  the  boilers,  or  for  any  other  pur- 
pose that  may  be  required. 

Several  engines  may  exhaust  into  one  condenser,  and 
a  single  pump  can  be  used  to  supply  several  condensers. 
The  injector  condenser  occupies  very  little  room,  and 
may  be  attached  to  the  engine,  in  the  most  convenient 
situation.  By  dispensing  with  the  air  pump  used  with 
ordinary  jet  condensers,  a  saving  in  power  is  obviously 
effected. 

A  stoppage  of  the  wattr  supply  merely  causes  the 
exhaust  steam  to  open  the  relief  valve  on  top,  and  thus 
pass  away,  but  caunot  endanger  the  safety  of  the  en- 
gine, by  allowing  water  to  enter  the  cylinder  of  the 
same. 


KNOWLES'     INDEPENDENT      JET     CONDENSER. 

Tig.  364  represents  a  Knowles  Independent  Jet  Con- 
denser attached  to  a  Corliss  Engine.  The  exhaust 
passes  through  the  pipe  x  into  the  heater  H,  and  thence 


into  the  condenser  C  which  is  upon  the  top  of  the  air 
pump,  which  discharges  the  products  of  condensation 
through  the  pipe  D. 

The  air  pump  is  driven  by  a  steam  cylinder,  whose 
action  is  described  with  reference  to  the  Knowles  steam 
pump.  The  exhaust  from  the  steam  cylinder  of  the 
condenser  passes  though  the  pipe  x  x  into  the  condenser 
itself,  hence  this  cylinder  also  receives  the  benefit  of 
the  vacuum.  The  injection  water  is  supplied  through 
the  pipe  I  near  the  top  of  the  condenser,  the  gate  valve 
for  opening  and  closing  the  same,  being  shown  at  G. 

The  feed  water  for  the  boiler  is  drawn  through  the 
suction  pipe  S,  and  is  forced  through  the  pipe  F1  to  the 
heater  H  where  it  passes  through  a  coil  of  pipe  that  is 
surrounded  by  the  exhaust  steam,  that  is  on  its  way 
from  the  main  cylinder  to  the  condenser,  and  that  enters 
at  one  end  of  the  heater  and  passes  out  at  the  other 
into  the  condenser.  The  feed  water  thus  extracts  heat 
from  the  exhaust  steam,  and  thus  helps  the  condenser. 
From  the  heater  the  feed  water  passes  through  the  pipe 
F  F  to  the  boiler;  at  T  is  the  valve  for  admitting  steam 
to  the  condenser  steam  cylinder,  hence  all  the  valves 
necessary  to  operate  the  condenser  are  contiguous  to 
the  engine.  Pipe  V  is  for  permitting  the  air  and  un- 
condensed  gases  exit  from  the  air  pump  being  carried 
up  beyond  the  level  of  the  pump  discharge  water. 

Fig.  365  represents  a  Knowles  independent  jet  con- 
denser with  safety-valve  and  float,  the  construction 
being  as  follows:  The  exhaust  steam  enters  at  I  and 
the  injection  at  F.  There  are  two  perforaied  discs  or 
water  dividing  plates,  one  of  which  is  above  the  steam 
inlet  I,  and  the  .other  below  it,  so  that  the  exhaust 
steam  meets  at  once  a  number  of  sprays  of  \v;iicr. 
The  lower  plate  has  at  its  center,  an  opening  bounded 
by  a  vertical  flange,  as  shown  in  the  figure,  and  steam 
passing  through  this  opening  meets  the  sprays  that  fall 
from  the  lower  perforated  disc.  The  water,  air,  and 
gases  are  drawn  off  by  the  air  pump  from  the  bottom 
of  the  condenser.  At  Z  is  a  valve  held  to  its  seat  by 
the  globe  shown  suspended,  which  is  hollow  and  light. 

Now  suppose  that  from  some  unusual  and  unexpected 
cause,  the  condenser  should  begin  to  fill  with  water, 
and  the  float  would  lift  the  valve  Z  and  destroy  the 
vacuum,  thus  stopping  the  inflow  of  injection  water, 
while  permitting  the  exhaust  steam  to  pass  out  at  L. 


TIII-: 


24!) 


I 


250 


STEAM  ENGINES. 


Fig.  364. 


Application,  Of  The  Rnou-les 


THE 


CONDENSER. 


251 


32 


Fig-  365. 

Knowles  Condenser  With  Safety  Valve. 


252 


MODERN  STEAM.  ENGINES. 


SURFACE  CONDENSER. 


A  general  view  of  Wheeler 's  Independent  Surface 
Condenser  is  given  in  fig.  3GG,  and  a  sectional  view  of 
the  same  in  fig.  3C7. 

The  condenser  is  mounted  horizontally  at  one  end  on 


The  circulating  pump  forces  the  injection  water 
through  the  tubes,  the  construction  being  as  follows: 

The  pistons  are  supposed  to  be  moving  in  the  stroke 
from  left  to  right,  hence  the  air  pump  is  drawing  out 
the  condensed  water  and  air  through  B,  and  through 
the  left  hand  suction  valve  S.  On  the  other  side  the 
air  pump  piston  is  forcing  the  discharge  through  the 
right  hand  delivery  valve  V.  Similarly,  the  circulating 


Fig,  366. 

WTieeler's  Independent  Surface  Condenser. 


the  circulating  pump,  and  at  the  other  on  the  air  pump. 
Both  pump  pistons  are  on  the  same  rod,  as  is  also  the 
piston  for  the  steam  cylinder  that  operates  both  pumps. 
The  exhaust  steam  enters  at  A  and  is  distributed 
along  the  condenser  by  the  perforated  plate  O,  beneath 
which  the  tubes  are  arranged.' 


pump  is  rccieving  the  injection  water  through  its  left 
hand  suction  valve  S,  and  forcing  it  through  the  right 
hand  valve  V  into  a  chamber  F.  which  is  separated 
from  the  chamber  II  by  a  partition  E,  thus  giving  two 
separate  systems  <:f  tubes  through  which  the  injection 
water  passes. 


CF 


\VIlEELELt' X  SURFACE  CONDEHSER. 


253 


to 

«0 


254 


MODERN  STEAM  ENGINES. 


The  Bulkley  Independent  Injector  Condenser. 


Fig.    368. 


EXHAUST 
FROM  ENGINE 


H.  W.  BULKLEY'S 
INJECTOR  CONDENSER 

AS  ARRANGED  WITH 
STEAM  PUMP 


,'  if    ,  •          y 

T~tHr-"$~~hr^- 

\     •     '    ''•'   /' 

>^  1 0°4i'-'-'''  .>?M  I — i 


'/'///•; 


L'OXDKXSER. 


255 


The  construction  whereby  the  injection  water  is  cir- 
culated from  end  to  end  of  the  tul»'s,  is  more  fully 
shown  at  tin-  bottom  of  Fiir.  :>(>7.  where  a  pair  of  t; 
are  shown  removed  from  the  condenser  and  turned  end 
for  end,  and  it  is  seen  that  there  are  two  tubes,  one 
within  the  other. 

The  plate  K  corresponds  to  the  inner  wall  of  cham- 
ber F,  in  the  sectional  view,  while  plate  J  is  the  inner 
wall  of  plate  G,  in  the  sectional  view.  The  injection 
water  enters  at  X  and  passes  through  the  inner  tube  M 
into  the  outer  tube  L,  and  takes  the  course  shown  by 
the  arrows,  'emerging  from  the  end  J,  and  passing 
through  the  opening  at  E  in  the  sectional  view,  from 
the  lower  to  the  upper  system  of  tubes,  which  corres- 
pond to  those  in  the  lower  system,  and  finally  passim: 
out  at  D.  At  Q  is  a  cap  that  may  be  removed  when 
the  tubes  are  to  be  cleaned. 

The  tubes  are  rigidly  held  at  one  end  by  the  plates 
J  K,  Fig.  3(>7,  while  at  the  other  they  are  supported  by 
plates,  shown  at  T  T  in  the  sectional  view.  This  per- 
mits them  to  expand  and  contract  freely,  and  obviates 
the  necessity  of  employing  the  paper  ferrules  that  are 
necessary  when  the  tubes  are  rigidly  held  at  both  ends, 
in  order  to  prevent  the  tubes  from  leaking,  and  from 
creeping  throngh  the  plates. 


Bulkleij's   Independent  Injector 
Condenser. 


Fig.  368  represents  Bulkley's  Injector  Condenser,  as 
arranged  with  air  and  injection  pumps.  The  construct- 
tion  of  the  condenser  corresponds  to  that  shown  in  Fig- 
355,  while  that  of  the  air  and  steam  pumps  is  as  fol- 
lows: The  steam  pump  is  shown  in  section,  and  the 
air  pump  with  the  valve  chest  cover  removed,  to  expose 
the  pump  valves.  Both  pistons  are  on  one  rod,  which 
vibrate  the  lever  I  and  through  the  medium  of  the  rod 
connection  at  m,  the  rod  L  which  is  supported  at  T  and 
has  tappets  t. 

The  valve  V  has  a  flat  face,  and  therefore  follows  up 
its  wear,  and  operates  over  three  ports  in  the  usual  man- 
ner. To  the  valve  spindle  is  attached  a  small  piston  C, 
operating  in  a  steam  chest  cylinder  attached  to  the  end 


of  the  rod  L,  at  r  and  *  are  two  small  ports,  which  con- 
nect with  the  exhaust  ]x>rt  e,  and  in  the  steam  chest 
cylinder  are  similar  ports.  In  the  face  of  the  seat  upon 
which  the  chest  cylinder  slides,  are  cut  two  recesses, 
through  which  the  ports  in  the  chest  cylinder  take 
steam,  as  they  pass  over  them.  Thus  in  the  end  view, 
it  is  seen,  that  two  ports  denoted  by  e  s  are  in  communi- 
cation. Now  suppose  the  next  piston  stroke  to  proceed, 
and  through  lever  I  and  rod  L  the  chest  cylinder  will 
move  to  the  left  until  it  meets  the  tappet,  whereupon  it 
will  move  the  chest  cylinder  to  the  right.  The  latter 
will  carry  with  it  the  chest  piston,  both  moving  together, 
until  such  time  as  the  port  in  the  chest  cylinder  comes 
opposite  to  port  r,  whereupon  steam  will  pass  through  r, 
and  between  the  chest  piston  and  cylinder,  and  the 
chest  piston  will  move  suddenly  to  the  left  hand  end  of 
its  cylinder,  opening  the  port  at  one  end  of  the  main 
cylinder  for  the  exhaust,  and  the  port  at  the  other  end 
for  the  admission,  and  thus  reversing  the  motion. 


The  Reynolds  Condenser. 


In  the  Figures  from  369  to  371  is  shown  the  conden- 
sing apparatus,  employed  by  E.  P.  Allis  &  Co.,  in  con- 
nection with  the  Reynolds'  Corliss  engine. 

The  exhaust  from  the  engine  cylinder  passes  first 
into  a  feed  water  and  purifier,  and  thence  to  the  jet 
condenser. 

THE  HEATER. 

The  construction  of  the  feed  water  heater  is  shown 
in  Fig.  369,  and  that  of  the  condenser  in  Figs.  370  and 
371.  In  the  heater  are  two  tube-plates  p  p  near  the  top, 
and  p  p  near  the  bottom. 

The  water  from  the  feed  pump  enters  the  pipe  A, 
passes  up  it  into  pipe  B,  and  descends  through  the 
annular  space  between  the  two  pipes,  into  the  space 
below  the  lower  tube-plate  p  p,  whence  it  passes  up  the 
tubes  to  the  top  of  the  heater,  where  it  enters  the  feed 
pipe  that  passes  to  the  boiler.  In  the  upper  chamber 
of  the  heater  is  the  scum  pan,  in  which  the  scum  of 


256 


MODEHX  STEAM  ENGINES. 


Fig.  369. 


ENGINE  CYLINDER 


Till-:  REYNOLDS  GONDENSBR 


"  i 


The  Reynolds  Condenser— Sectional  View. 


Fig.   370. 


Of  THE 

(UNIVERSITY, 


258 


Till:  REYNOLDS  CONDENSER. 


25'J 


tin'  water  accumulates,  and  from  which  it  is  occasionally 
lilnwii  off  through  the  pipe  shown,  tin-  lower  end  of 
which  enters  the  scum  pan. 

The  settlings  from  the  leed  water  may  also  be  blown 
off  through!:  own  at  the  bottom  of 

the  heater. 

The  exhaust  steam  from  the  engine  cylinder  enters 
on  one  side  iieiieatli  thr  upper  tube  plate  p,  and  leaves 
through  the  jiipe  T  aliove  the  lower  tube-plate,  passing 
'ice  into  the  condenser. 


THE  CONSTRUCTION  OF  THE  CONDENSER. 

A    sectional   view  of  the  condenser  is  shown  in   Fig. 
370,  and  a  plan   partly  in  section  in  Fig.  371. 

Referring  lirst  to  the  sectional  view.  Fig.  370,  the  pipe 
T  corresponds  lo  pipe  T  in  Fig.  3(J!).  in  which  is  a  valve 
K  for  stopping  off  communication  with  the  condenser, 
if  it  should  be  required  to  use  the  engine  for  non-con- 
di using;  V  is  a  relief  valve  that  when  the  condenser  is 
in  operation  is  held  closed  by  the  vacuum,  but  that 
may  open  by  means  of  the  lever  L,  to  permit  the 
exhaust  from  the  engine  to  pass  up  the  high  pressure 
exhaust  pipe  when  K  is  closed,  or  in  case,  from  some 
cause  or  other,  the  vacuum  should  be  lost,  or  the  con- 
denser flooded  with  water. 
33 


The  spray  plate  (shown  in  section,  at  S  in  Fig.  371) 
extends  partly  around  the  condenser,  the  injection  water 
entering  above  it  at  J.  This  plate  therefore  divides  the 
injection  water  into  fine  streams,  which  fall  down  the 
condenser  and  condense  the  steam.  The  water  of 
condensation  falls  to  the  bottom  of  the  condenser,  and 
the  air  and  gases  remain  above  it  until  removed  by 
the  air  pump.  The  capacity  of  the  air  pump  is  suffi- 
ciently great  to  discharge  the  injection  water,  the  water 
of  the  condensed  steam,  and  also  the  air  and  gases,  as 
fast  as  they  are  separated  from  the  steam,  aDout  ^  of 
the  pump  capacity  being  filled  with  water  at  each 
upward  or  drawing  stroke. 

The  suction  valves  V  V  are  in  the  piston,  or  bucket 
of  the  air  pump,  and  the  discharge  valves  V*  V*  in 
the  cover  at  the  top  of  the  pump.  These  valves  consist 
of  flat  rubber  discs  upon  a  central  stem,  having  at  its 
top  a  dish  shaped  shield,  which  limits  the  amount  to 
which  the  valve  can  open.  A  spiral  spring  at  the  back 
of  the  valve  closes  it  to  its  seat.  The  same  form  of 
condenser  is  used  whether  it  be  driven  by  belt  connec- 
tion to  the  pulley  wheel,  or  whether  the  same  be  driven 
by  a  steam  cylinder  attached  to  the  side  of  the  conden- 
ser. 

The  weight  of  the  crank,  etc.,  is  counter- balanced  by 
a  weight  on  the  pulley  wheel. 


CHAPTER  X. 


COMPOUND  CONDENSING  AND  TRIPLE  EXPANSION  STATIONARY  ENGINES. 


Figs.  372,  373,  and  374  represent  the  "Worthington 
Compound  Condensing  Engine,  for  the  water- works  of 
towns  and  cities.  It  consists  of  a  pair  of  engines  and 
pumps  placed  side  by  side,  but  forming  virtually  one 
engine  because  the  valves  for  one  engine  are  operated 
from  the  piston-rod  of  the  other,  while  both  pumps 
discharge  through  a  common  delivery  pipe. 

The  distinguishing  features  of  this  engine  are,  first, 
that  the  water  is  given  a  continuous  and  as  nearly  as 
possible,  a  uniform  flow  through  the  suction  and  deliv- 
ery pipes,  its  path  of  motion  being  kept  as  nearly 
straight  as  possible,  and  secondly,  that  the  valves  are 
permitted  to  close  without  the  violence  that  is  found  to 
prove  destructive  in  some  kinds  of  pumps. 

This  is  accomplished  by  the  peculiar  construction 
and  arrangement  of  the  steam  valve  gear,  and  by  the 
arrangement  of  the  pump  valves.  The  valve  gear  is 
such  as  to  cause  the  pistons  to  pause  at  the  end  of  each 
stroke,  thus  permitting  the  pump  valves  to  seat  them- 
selves quietly,  and  therefore  without  inducing  reverse 
currents  in  the  water,  or  checking  its  continuous  flow 
through  the  main. 

The  construction  of  the  steam  end  of  the  engine  is 
shown  in  section  in  Fig.  373,  H.  P.  is  the  high  pressure 

piston  whose  rod  attaches  direct  to  the  pump  plunger, 
200 


L.  P.  is  the  low  pressure  piston,  which  has  two  rods  R 
connecting  to  the  cross-head  C',  at  R. 

The  stretcher  rods  or  tie  rods,  S  R,  tie  the  steam  and 
water  cylinders  together  and  keep  them  in  line.  At  G 
is  the  guide-bar  for  cross-head  C',  which  (by  means  of  a 
short  rod)  drives  the  bell  crank  B',  which  operates  the 
pair  of  air  pumps  that  are  shown  in  section.  Cross-head 
C  drives  bell  crank  B,  which  works  the  air  pump  for 
the  other  engine.  From  bell  crank  B',  a  rod  V  actuates 
a  rock-shaft,  which  operates  the  valve  motion  for  the 
back  pair  of  cylinders.  The  valve  motion  for  the  H.  P. 
and  L.  P.  cylinders  of  the  engine  that  is  shown  in  section 
may  be  traced  as  follows:  The  bell  crank  B  actuates 
the  rod  b  which  operates  the  rock-shaft  r,  which  con- 
nects at  W  to  the  rod  for  the  two  steam  valves.  These 
two  valves  are  balanced  by  a  pendulum  p,  pivoted  at  its 
upper  end,  and  having  at  its  lower  end  a  piston  fitting 
a  bore  in  the  back  of  the  valve.  Beneath  each  balan- 
cing piston  there  is  an  opening  leading  into  the  ex- 
haust, hence  the  valves  must  be  balanced,  notwithstand- 
ing any  wear  that  might  in  time  occur  in  the  valve 
balancing  pistons. 

In  each  cylinder  the  end  ports  as  S  S',  are  the  steam 
ports,  the  inner  ports  e  e  and  e'  e'  being  for  the  ex- 
haust. The  exhaust  from  the  high  pressure  cylinder 


COMPOUND  CONDSDS1NQ  EX U INK. 


261 


MODKRN  KTEAM  ENGINES. 


Worthingtorfs  Compound  Condensing  Engine. 


Fig.   373. 


COMPOUND  co\in:\si\i;  !•:  .\  < ;  i  .\  i-; 


•263 


passes  through  pipe  E  to  the  steam  chest  E'  of  the  low 

-sure  cylinder,  where  il  is   superheated   liy  the   p 
at  J,  wlr.'  ii   live  steam  at  or  near   boiler   p 

sure.  The  exhaust  from  the  lo\v  pressure  cylinder 
e<  out  at  K-1.  and  through  the  pipe  K*  to  the  con- 
dense]-, where  it  meets  the  injection  water,  the  jet  being 
divided  up  by  means  of  perforated  plates,  which  separate 
it  into  small  stream-,  a-  shown.  From  the  bottom  F  of 
the  condenser,  the  water,  air  and  L  o  the,  air 

pumps  at  D.  At  c  and  a'  are  the  foot  valvos,  «  living 
shown  open  to  admit  ingress  to  air  pump  />  which  is 
ascending.  The  air  pump  piston  j/  is  descending, 
lience  its  foot  valve  /•'  is  close.!,  while  the  valves  in  // 
are  open,  the  air,  gas  and  water  passing  1'roiu  the  lower 
to  the  upper  side  of  the  piston.  The  air  pump  dis- 
charge occurs  through  the  openings  at  f  and  c'.  The 
trunk  pisto»-n>ds  render  guides  for  the  air  pump  pistons 
unnecessary,  and  enable  the  use  of  long  rods  from  the 
bars  15  B'.  thus  avoiding  side  strains. 

lla\  '.-d   the  general    construction    of    the 

engine,  we  may  now  pass  to  the  construction  whereby 
the  pistons  are  caused  to  pause  at  the  ends  of  their 
strok 

The  steam  valves  have  no  lap,  hence  the  steam  fol- 
lows full  stroke,  while  the  exhaust  passages  being  closed 
as  the  pistons  pass  over  them,  a  certain  amount  of  com- 
pression is  obtained.  As  both  valves  are  alike,  and 
are  operated  by  the  same  rod.  we  may  follow  the  motion 
with  reference  to  the  L.  P.  cylinder,  only  the  descrip. 
tion  answering  for  both.  The  cross-head  C,  on  revers- 
ing its  motion,  operates  (through  the  medium  of  13  and 
b)  the  rocker  r,  which  connects  at  W  to  the  valve  rod. 
There  is.  however  at  W,  a  certain  amount  of  lost  motion, 
so  that  the  motion  of  r  may  continue  for  a  certain 
period  without  operating  the  valve,  and  during  this 
period,  steam  port  S'  remains  fully  opened. 

When  the  lost  motion  or  play  at  W  is  taken  up.  the 
valve  will  move  to  the  left,  and  by  the  time  the  piston 
has  nearly  completed  its  stroke,  the  left  hand  steam 
port  s'  will  be  closed,  and  its  adjacent  exhaust  port  e, 
opened. 

Simultaneously,  at  the  other  end  of  the  cylinder,  the 
steam  port  will  be  opened,  and  its  exhaust  port  e  closed. 

On  account  of  the  position  of  the  attachment  of  the 
rod  b  on  bell  crank  B,  and  of  the  small  amount  of  valve 


travel,  the  port  opening  is  so  regulated,  that  it  takes  a 
certain  amount  of  time,  after  ttie  piston  has  stopped, 
before  there  is  steam  pressure  enough  to  start  the  pis- 
ton  "ii  its  return  stroke,  and  this  gives  the  pause,  or 
period  of  rest,  before  referred  to. 

We  have  here  considered  the  action  of  one  engine 
only,  and  it  will  be  readily  perceived,  that  as  cross-head 
C'  is  at  half-stroke  when  C  is  at  the  end  of  its  stroke, 
therefore  one  engine  takes  up  the  motion  before  the 
other  pauses,  this  action  following  in  regular  rotation, 
so  that  the  water  is  drawn  up  the  suction  pipe,  arid 
forced  through  the  delivery  pipe,  with  a  constant  and 
unchecked  How. 

The  duration  of  the  piston  pause  at  the  end  of  the 
stroke,  may  obviously  be  regulated,  by  adjusting  the 
amount  of  lost  motion  at  W,  because  the  greater  the 
amount  of  lost  motion,  the  later  the  port  is  opened,  and 
the  longer  the  pause.  In  addition  to  this,  however, 
valves  are  employed,  by  means  of  which  the  steam  and 
exhaust  ports,  at  each  end  of  the  cylinder,  may  be  plac- 
ed into  communication,  so  that  after  the  piston  has  clos- 
ed the  exhaust  port,  the  compressed  steam  may  pass 
from  the  steam  port  into  the  exhaust,  to  relieve  the 
compression  if  necessary,  and  thus  permit  the  piston  to 
travel  the  full  length  of  stroke. 

The  construction  of  the  pump  is  shown  in  Fig.  374. 
The  length  of  the  water  cylinder  is  divided  into  two 
divisions,  A  and  A',  the  plunger  working  through  a 
bushing,  as  shown  at  r.  The  suction  chamber  extends 
beneath  the  full  length  of  the  pump.  The  suction 
valves  extend  along  the  bottom,  and  the  delivery  valves 
along  the  top  of  the  pump  cylinder.  The  plunger  is 
supposed  to  be  moving  from  left  to  right,  lience  divi- 
sion A  is  receiving  water,  and  division  A'  delivering  it, 
as  denoted  by  the  arrows.  The  water,  it  will  be  obser- 
ved, can  pass  through  the  pump  in  a  straight  line,  ex- 
cept in  so  far  as  it  is  deviated  therefrom,  by  passing 
around  one  side  of  the  plunger  circumference.  The 
valves  are  flat  rubber  discs  guided  by  a  central  stem, 
and  seated  by  means  of  a  spiral  spring  at  the  back  of 
each  valve. 

Hand  holes  are  provided,  to  afford  access  to  the  pump 
valves.  The  delivery  pipe  from  each  pump  connects 
to  a  central  pipe,  on  which  the  air  chamber  is  situated, 
so  that  the  one  air  chamber  serves  for  both  pumps. 


Fig.   374. 


264 


CUMPOl'XD   ro>.\7'/:.y.s7.Y'/ 


Vertical  Com  pound  Cuiiilcnxiitg  l.ii>J.iiic. 

r'ii;.     .'!".">.    (which     is    extruded    from   tin-    /•.';/<///<•</•) 
represents  11  cuinjiouinl  condensing   eugino  with  surface 


In  this  cMirinr  ;i  double  acting  bucket  pump  serves 
for  both  the  circulating  ami  the  air  pump,  ihe  construc- 
tion iii-ing  as  follows:  The  condenser  C  is  in  the  base 
of  one  t'nniH1.  the  jmnip  being  worked  from  the  engine 
iirii'l.  !>y  means  of  beams  A,  and  rods  P. 

The  pump  is  divided  into  two  compartments,  each. 


Fig.  375. 


condenser,  constructed  by  Worth,  Mackensie  &  Co. 
The  two  cylinders  are  in  line  with  their  pistons  on 
one  rod,  and  are  separated  so  that  the  upper  gland  of 
the  L.  P.  and  the  lower  one  of  the  II.  1'.  cylinder,  may 
be  accessible  for  adjustment. 


having  its  own  pair  of  valves,  of  which  the  lower  of 
each  pair  is  the  suction,  and  the  upper  the  delivery 
valves,  the  lower  pair  are  for  circulating,  and  the  upper 
for  the  air  pump,  hence  each  of  them  is  single  acting, 
while  the  pump  bucket  li  is  double  acting,  effecting  on 


266 


MODERN  STEAM  ENGINES. 


each  stroke  the  suction  of  one,  and  the  delivery  of  the 
other  pump. 

Triple    Expansion    Stationary 
Engines. 

Figs.  376,  376«,  3766,  376c,  376d,  represent  a  triple 
expansion  engine  for  driving  mills,  which  was  exhib- 
ited at  the  Paris  Exhibition  of  1889.  This  engine  has 
four  cylinders,  the  high-pressure  and  intermediate  cyl- 


Fig.  376d. 

inders  respectively  marked  H.  P.  and  I.  P.  being 
nearest  to  the  crank,  while  the  two  low-pressure  cylin- 
ders marked  L  P  and  L  P'  are  in  the  rear,  and  are 
of  unequal  diameters. 

By  this  arrangement  there  are  obtained  two  en- 
gines, either  of  which  may  be  used  as  an  indepen- 
dent tandem  compound  engine  in  case  of  accident,  or 
•which  may  be  worked  coupled  as  tandem  compounds 
(there  being  in  the  latter  case  two  high  and  two  low- 
pressure  cylinders),  in  case  of  circumstances  necessi- 


tating  a  reduction  of  boiler  pressure  below  that  suit- 
able for  the  triple  expansion  system  of  working. 

The  engine  is  thus  available  for  working  in  three 
different  ways,  the  necessary  changes  in  the  mode  of 
working  being  made  by  means  of  the  arrangement 
of  the  pipes  and  valves  connecting  the  cylinders. 

The  valve  gear  is  shown  in  Figs.  376,  376a  and 
3766,  and  a  longitudinal  sectional  view  of  the  cylin- 
ders in  Fig.  376c. 

Fig.  376  shows  the  engine  from  the  side  on  which 
the  exhaust  valves  are  placed.  Fig.  376a  is  a  plan 
and  Fig.  3766  a  side  elevation  showing  the  connec- 
tions from  the  eccentric  to  the  steam  valves,  the  con- 
nections from  the  eccentrics  for  the  steam  and  ex- 
haust valves  combined  being  shown  in  Fig.  376a. 

Referring  to  the  steam  valves  independently  of  the 
exhaust  valves,  A,  Fig.  3766,  is  the  eccentric  rod 
operating  a  rock  shaft  B,  which  at  its  lower  end  op- 
erates the  rod  C,  vibrating  the  rock  shaft  D,  which 
works  the  rods  E  and  F  for  the  live-steam  valves  a  and 
6.  The  lower  end  of  the  rock  shaft  D  works  a  rod  G, 
which  connects  to  a  rock  shaft  H,  which  operates 
the  rods  J,  K  for  the  steam  valves  c  d  for  the  low- 
pressure  cylinder. 

The  rod  G  is  shown  dotted  in  Fig.  3766,  but  as  it 
is  below  the  bed-plate  of  the  engine  is  not  seen  in 
Fig.  376a. 

The  manner  in  which  the  exhaust  valves  are 
worked  is  as  follows  : 

Referring  to  Fig.  376a,  L  is  the  eccentric  rod  for 
the  exhaust,  being  connected  to  the  rocker  M  operat- 
ing the  rod  M',  which  operates  the  rocker  N',  which 
is  fast  upon  its  shaft.  This  shaft  passes  beneath  the 
engine  cylinder,  and  operates  at  its  other  end  the 
rocker  N",  which  drives  the  rods  O,  P  for  the  high 
pressure  exhaust  valves. 

The  lower  arm  of  the  rocker  N"  operates  a  rod  Q, 
Fig.  376,  which  connects  to  the  lower  end  of  the 
rocker  R,  and  the  rods  S,  T  drive  the  valves  g,  h, 
for  the  exhaust  valves  of  the  low-pressure  cylinders. 

The  valves  on  the  high-pressure  cylinder  are  pro- 
vided with  a  cut-off  gear  of  the  Corliss  type  controlled 
by  a  Porter  governor.  The  valves  are  opened  by  the 
eccentric  and  closed  for  the  cut-off  by  the  action  of  a 
spring  as  soon  as  they  are  released  by  the  detent,  the 


TRIPLE  EXPANSION  STAriUXAHY  EXGLVES. 


267 


/•^eSE    LI 

f  OF  THE 

(TJNIVERSITT 

\-J 


268 


MODERN  STEAM  ENGINES. 


TKWLE  EXrA.\SK>.\ 


K\<ll\ES. 


270 


MODERN  STEAM 


construction  of  which  is  shown  in  Fig.  376y.      The 
point  in  the  piston  stroke  at  which  the  detent  is  re- 


Fig.  376«. 

leased  and  the  valve  closed  for  the  cut-off  depends 
upon  what  part  of  the  cam  acts  upon  the  releasing 
rods. 

The  air  pumps  are  driven  by  a  lever  V,  Fig.  376, 
actuated  by  the  cross-head  of  the  engine.  Detail 
views  of  one  of  the  air  pumps  are  given  in  Figs.  376d 
and  376e,  while  Fig.  376/ shows  one  of  the  air  pump 
valves.  The  plunger,  which  is  of  conical  form  at  its 
lower  end,  operates  in  a  cylinder  surrounded  by  an  an- 
nular chamber,  which  is  divided  into  two  parts,  W  and 
X,  376d,  the  lower  of  which  (W)  forms  the  condenser 
and  the  upper  the  hot  well.  This  chamber  is  seated 
on  a  hemispherical  casting,  into  which  the  bottom  of 
the  air  pump  cylinder  opens,  the  top  of  this  casting 
carrying  valves  opening  downwards  to  admit  the 


Fig.  376f. 

steam  nnd  upwards  to  deliver  the  products  of  con- 
densation. 

An  example  of  a  triple  expansion   stationary  en- 


Fig.  376/7. 

gine  in  which  the  cylinders  are  arranged  one  above 
the  other  is  given  in  the  following  figures : 

Fig.  376A  shows  the  engine  from  one  side,  and  Fig. 
376i  from  the  other. 

All  three  of  the  cylinders  have  their  piston-rods 
attached  to  a  vertical  crosshead  A,  whose  gudgeon 
affords  journal  bearing  for  the  connecting  rod,  and  it 
is  obvious,  therefore,  that  all  three  pistons  move 
simultaneously  in  the  same  direction. 

The  high-pressure  cylinder  is  the  uppermost,  steam 
passing  thence  to  the  intermediate  cylinder,  and 
from  it  to  the  low-pressure  cylinder,  which  is  secured 
at  the  bead  end  to  the  foundation. 

The  construction  of  the  valve  gear  is  as  follows: 

The  steam  valves  for  the  high-pressure  cylinder 
are  of  the  Corliss  type,  and.  referring  to  the  live  steam 
valves  J  and  L  in  Fig.  376i,  the  eccentric  B  operates 
the  rod  C,  which  connects  to  a  rocker  e  operating  the 
rod  F  connected  to,  and  therefore  vibrating  the  wrist 
plate  G,  from  which  rod  H  operates  the  valve  at  J, 
while  rod  K  from  the  same  wrist  plate  operates  the 
valve  at  L.  The  dash  pot  for  valve  J  is  shown  at  I, 
and  that  for  the  valve  at  L  is  shown  at  M. 

The  valves  at   T  and   V,   which    are  the  exhaust 


A'.V/M.VN/O.V   STATH).\AliY 


27; 


V*  4; 


372 


MODERN  STEAM  ENGINES. 


t--. 

CO 

I? 


TRIPLE  EXPANSION  STATIONARY  ENGL\E*. 


273 


Spring  recoil 
(0  kttf  Catiti  10 1 


Dash  foi  Hod  ri 

ouplut  u>  inn 

«n  '  '  • 
Cnernor 


connac 
9ltuip» 

TiT 

T 

ft«        ra'rf  fvi  Opn/)tf 
j-         „  „...        ..  ,  ,,^WT^_ 

i 
) 

1  —    r^ 

£ 

o 

-• 

V.  f 

Wtf- 

-W 

Wvn  ipi/u/o 
J 

J 

S—  r 

i!  it      n 

fy.  376;. 
Talve  of  the  high   pressure,  are  worked  from   the  eccentric  X,  which  operates  rod  N,  which  connects 

tine  of  Sttafrt  Pressure  in  pipe 


Line  of  flreMurg  In  Steam  pipe 


Engine  4  Ft    stroke. 
U  revolubonf  per  mm 

I  HP  S3  3& 


High  Prenurt  Cylinder.  &'/•  dia      Scale  '/no 


Front 


Intermediate   Cylinder,  I3'4    dm        Scale  'A» 
l.H.P  66  Z 


Bach 


Total  l.H.P      167   6 


Lo»  Pressure    Cylinder.   2l>t' dia     Scale   '/to 

Fig.  376i. 

to  the  rocker  P,  whose  lower  arm  drives  the  rod  Q,  I      Referring    now  to  Fig.   376A,  which    shows    the 
operating  the  wrist  plate  R.  I  valve  gear  for  the  intermediate  and  for  the  low- 


274 


MODERN  STEAM  ENGINES. 


pressure  cylinder  a,  is  the  eccentric  rod  for  driving 
the  admission  valve,  which  is  a  flat  or  common  D 
valve,  and  6,  the  eccentric  for  driving  the  cut-off'  valve, 
and  also  the  lever  c,  which  at  its  lower  end  drives  the 
exhaust  valve  for  the  low-pressure  cylinder.  Fig. 
376;  represents  detail  views  of  the  trip  gear  for  the 
high-pressure  cylinder.  The  discs  on  which  are 
mounted  the  tripping  arrangements  are  made  of 
wrought-iron  forged  plates.  The  pawl  is  of  steel,  and 
is  fitted  with  a  steel  pin  1  in.  in  diameter ;  on  the 
same  axis  is  also  fitted  the  cam  and  lever  for  tripping 
the  pawl,  which  is  of  steel,  case-hardened.  The 
wrist  plates  are  of  cast  iron  bushed  with  steel  liners 
and  fitted  with  11  in.  steel  case-hardened  pins.  The 
details  of  construction  of  this  trip  gear,  which  is  the 
designer's  special  pattern,  are  clearly  shown  by  the 
engravings  in  the  adjoining  column. 

The  crosshead  is  fitted  with  a  steel  gudgeon,  5J  in. 


in  diameter  in  the  body  and  4|  in.  in  diameter  in  the 
necks,  with  outer  necks  2J  in.  in  diameter  by  2J  in. 
long,  for  the  air  pump  links.  The  connecting  rod  is 
10  ft.  long,  4j  in.  in  diameter  at  the  crosshead  end, 
41  in.  in  diameter  at  butt  end,  and  5}  in.  in  diameter 
in  the  centre,  forked  at  the  crosshead  end  and  solid  at 
the  butt  end.  The  fork  end  is  fitted  with  a  wrought- 
iron  cap  and  four  It  in.  bolts  and  lock  nuts.  The 
butt  end  is  fitted  with  a  steel  block,  die,  and  brasses, 
with  li  in.  steel  adjustment  screw. 

The  crank  is  6  in.  broad,  turned  and  polished  all 
over,  and  fitted  with  a  steel  pin  4J  in.  in  diameter  by 
6  in.  long,  with  an  outer  neck  for  the  drag  crank.  The 
crankshaft  is  9  in.  in  diameter  in  the  body  and  8i  in. 
in  diameter  by  14  in.  long  in  the  bearing  for  the  crank, 
pedestal,  and  10  in.  in  diameter  for  flywheel. 

A  set  of  diagrams  from  this  engine  is  given  in  Fig. 


CHAPTER    XI. 


THE    MA  KINK    ENGINE. 


THE  term  Marine  Engine  is  applied  in  a  general 
sense  to  the  engines  of  vessels  for  service  upon  salt 
water,  but,  by  a  more  strict  definition,  it  applies  to 
vessels  that  make  long  voyages  on  the  open  sea  or 
ocean. 

Marine  engines  are  either  compound  engines  with 
surface  condensers  or  triple  or  quadruple  expansion 
engines  with  surface  condensers.  Triple  expansion 
engines  have  displaced  compound  marine  engines  in 
all  large  ocean-going  steamships  on  account  of  the 
greatereconomy  of  fuel  consumption.  This  economy  is 
due  to  two  causes,  viz. :  it  permits  of  the  employment 
of  higher  pressures  of  steam  without  exhausting  at  a 
high  pressure,  and  it  enables  the  steam  to  be  used 
throughout  a  considerable  range  of  expansion  with- 
out being  subject  to  the  cooling  effect  of  the  con- 
denser. 

In  a  simple  high-pressure  or  single  cylinder  engine 
the  cylinder  is  cooled  during  each  exhaust  period ; 
first,  by  the  reduction  of  the  temperature  of  the  steam 
during  the  expansion,  and  secondly,  by  the  exhaust 
being  open  to  the  atmosphere,  which  with  the  ordi- 
nary forms  of  link  motion  extends  throughout  a 
larger  proportion  of  the  stroke  in  proportion  as  the 
point  of  cut-off  occurs  earlier  in  the  piston  stroke. 
Furthermore,  with  the  common  D  valve,  whether 
operated  direct  from  the  eccentric  or  through  the 


medium  of  a  link  motion  or  its  equivalent,  the  steam- 
port  does  not  open  sufficiently  to  admit  of  a  full 
supply  of  steam,  and  it  is  for  this  reason  that  double 
ported  valves  are  employed.  But  whatever  means 
may  be  employed  to  obtain  a  full  supply  of  live 
steam,  the  fact  remains  that  the  range  of  temperature 
in  the  high-pressure  cylinder  must  increase  in  pro- 
portion as  the  point  of  cut-off  occurs  earlier  in  the 
piston  stroke,  producing  a  corresponding  increase  in 
the  condensation  of  the  steam. 

In  triple  expansion  engines  the  live  steam  follows 
the  piston  throughout  the  greater  portion  of  the 
stroke,  as  from  I  to  J  stroke,  and  as  a  result  the  range 
of  temperature  is  in  this,  the  H.  P.  cylinder,  reduced 
to  a  minimum.  In  the  next  place  the  exhaust  from 
the  high-pressure  cylinder  in  a  triple  expansion 
engine  is  separated  by  the  intermediate  cylinder 
from  the  cooling  effects  of  the  condenser,  and  this 
again  acts  to  preserve  the  temperature  of  the  high- 
pressure  cylinder. 

Coming  now  to  the  intermediate  cylinder  there 
is  between  it  and  the  condenser  the  low-pressure 
cylinder,  which  serves  to  protect  the  steam  in  the 
intermediate  cylinder  from  the  cooling  effects  of  the 
condenser. 

In  an  article  upon  the  Inman  and  International 
steamship  City  of  New  York,  "  Engineering,"  of  March 

275 


276 


MODERN  STEAM  ENGINES. 


1,  1889,  says  that  the  same  amount  of  steam  will 
give  twenty  per  cent,  more  power  in  a  triple  expan- 
sion than  it  would  in  a  compound  engine. 

An  example  of  a  compound  condensing  marine 
engine,  as  made  in  the  smaller  sizes,  is  given  in  Fig. 
377,  in  which  H.  P.  is  the  high  and  L.  P.  the  low- 
pressure  piston,  and  S  the  receiver,  the  cranks  C  C' 
being  at  a  right  angle  one  to  the  other. 

The  exhaust  from  the  H.  P.  steam  passages  e 
passes  direct  into  the  receiver  S,  and  is  distributed  to 
the  L.  P.  piston  by  the  valve  V. 

The  H.  P.  cylinder  is  provided  with  a  double 
ported  main  valve  V  and  a  Meyer's  cut-off  valve  v, 
and  the  L.  P.  cylinder  with  a  double  ported  single 
valve  V. 

The  valves  V  for  the  high  and  v  for  the  low-press- 
ure cylinder  are  provided  with  pressure-relieving 
plates  on  their  backs.  The  two  main  valves  V  and 
V  respectively  are  driven  by  a  link  motion,  which  is 
used  for  reversing  purposes  only,  the  point  of  cut-oil' 
being  varied  by  the  cut-off  valve  of  the  H.  P.  cylin- 
der, which  is  driven  by  an  eccentric  D  set  opposite  to 
the  crank  C.  This  eccentric  operates  at  G  an  arm, 
which  is  pivoted  at  one  end. 

The  cut-off  valves  are  moved  upon  the  rod  to  vary 
the  point  of  cut-off  by  a  right  and  left  hand  screw,  as 
shown,  the  rod  having  journal  bearing  in  a  sleeve  S, 
so  that  it  may  be  revolved  in  S  by  a  hand  wheel 
operating  a  bevel  pinion  that  engages  with  the  bevel 
pinion  at  J. 

The  link  motions  for  the  main  valves  V  V  are 
moved  for  reversing  by  arms  from  the  shaft  H,  which 
lias  an  arm  that  is  operated  by  the  small  steam 
engine  shown  at  K.  This  small  reversing  engine  is 
also  provided  with  a  link  motion,  which  is  reversed 
by  a  hand  lever,  whose  rod  is  shown  at  r. 

The  weight  of  the  valves  and  their  connections  are 
counter-balanced  by  means  of  small  pistons  at  P  and 
P',  which  receive  the  pressure  of  the  steam  on  their 
lower  faces,  the  cylinders  or  cases  in  which  they 
work  being  open  at  the  top. 

At  R  R'  and  R"  are  relief  or  snifter  valves  which 
open  to  permit  the  escape  of  any  water  with  which 
the  respective  cylinders  may  become  charged.  These 
valves  are  usually  so  adjusted  by  either  a  weight  and 


lever,  or  a  spiral  spring,  that  they  only  open  under  a 
pressure  greater  than  the  highest  steam  pressure  the 
cylinders  receive. 

The  surface  condenser  M  is  shown  at  the  back  of  the 
engine,  its  pumps  being  operated  by  beams  worked 
from  the  rods  N,  which  receive  motion  from  the  cross- 
head  of  the  low  pressure  piston  as  shown  in  the 
figure. 

Fig.  378  represents  a  small  Marine  Engine,  in 
which  the  power  required  to  operate  the  link  motion 
is  small  enough  to  permit  its  being  shifted  by  a  hand 
lever  H,  which  operates  a  shaft  S,  having  arms  A  A 
that  shift  both  links  simultaneously  through  the 
medium  of  the  straight  links  e.  The  condenser  is 
shown  at  C,  the  air  and  circulating  pumps  being 
operated  by  the  levers  H  which  are  worked  by  short 
rods  li  from  the  low  pressure  cross-head. 

At  P  is  a  by-pass,  pass-over,  or  starting  valve,  that 
is  opened  to  admit  live  steam  into  the  receiver,  and 
thus  use  the  low  pressure  cylinder  as  a  high  pressure 
one,  until  the  engine  is  started. 

The  starting  valve  enables  the  engine  to  he  started 
when  the  high  pressure  piston  is  at  the  end  of  its 
stroke,  or  when  the  high  pressure  piston  alone  would 
not  be  powerful  enough.  Moreover,  when  the  air 
pump  is  driven  by  the  engine,  and  not  independently, 
the  vacuum  becomes  lost  after  the  engine  stands 
still. 

These  conditions  render  a  pass-over  or  starting 
valve  necessary.  The  starting  valve  is,  in  this 
example,  placed  outside  of  the  cylinder,  and  passes 
the  live  steam  from  the  H.  P.  steam  chest  into  the 
receiver,  but  in  some  cases  there  is  al«o  a  pass-over 
valve  in  the  passages  of  the  H.  P.  cylinder  (as  well 
as  into  the  L.  P.  cylinder),  so  as  to  admit  steam  to 
the  same  when  the  engine  stops  in  such  a  position, 
that  the  H.  P.  valves  have  effected  the  cut-off. 

Obviously,  however,  under  this  latter  condition 
alone  the  engine  might  (with  a  link  motion  easily 
operated  by  hand)  be  started,  by  operating  the  link 
motion  at  first  to  move  the  engine  in  the  wrong 
direction,  and  enough  to  open  the  steam-port  at  the 
other  end  of  the  cylinder  and  by  again  operating  the 
link  motion,  start  the  engine  in  the  required 
direction,  but  it  is  necessary  to  provide  means  by 


THE  MMti\t:  !•:. \ai\E. 


•J77 


i, 


278 


MODERN  STEAM  EXGIA'ES. 


Small  Marine  Engine, 


THE  AIAKIXK   KMIISK. 


27* 


which  the  engine  may  be  started  quickly,  and  in  the 
required  direction,  and  these  ends  are  accomplished 
by  means  of  the  pass-over  or  starting  valve.  It'  the 
vacuum  is  kept,  and  the  engine  is  in  such  a  position, 
that  the  live  Steam  Can  be  admitted,  tin' starting  valve 
need  not,  in  some  cases,  be  resorted  to. 

At  15  is  an  oil  box  from  which  pipes  lead  to  the 
various  working  parts  of  the  engine.      The  slots  D  : 
are  for  the  insertion  of  a  bar  to  move  the  engine  by  j 
hand,  for  setting  the  valves,  or  for  other  purpn 
The  high  and  low   pre.-sure  cylinders  are  provided 
with  waste  water  cocks  operated  separately  by  hand, 
whereas  in  larger  engines  all  these  coeks  are  connected 
to  one  lever,  whereby  they  may  be  opened  or  closed 
simultaneously. 

Fig.  379  represents  a  Marine  Engine,  such  as  is  used 
for  coasting  vessels.  Each  cylinder  has  its  link 
motion  which  is  shifted  by  a  common  tumbling 
shaft,  which  is  operated  by  the  hand  wheel  shown. 
The  link  motions  are  employed  to  vary  the  points  of 
cut-off,  as  well  as  for  reversing,  flat  slide-valves  being 
used. 

The  right  hand  handle  A  is  for  the  throttle  valve 
V  of  the  high  pressure  cylinder,  while  the  left  hand 
handle  R  operates  the  rod  shown  connected  to  the 
shaft  T,  an  arm  from  which  works  the  starting,  pass- 
over  or  by-pass  valve  at  D. 

The  middle  handle  C  operates  the  shaft  S,  that 
works  the  waste  water  cocks  for  the  two  cylinders. 
The  link  motions  are  shifted  simultaneously  as  fol- 
lows: The  wheel  W  operates,  by  a  worm  and 
worm-wheel  connection,  the  lever  L,  which  has  at  its 
upper  end  rods  passing  to  the  back  of  the  engine, 
where  they  operate  a  shaft  S,  upon  which  are  arms 
M  connected  to  links  or  arms  N,  which  shift  the 
links. 

Two  beams,  one  of  which  is  seen  at  A,  operate  the 
air  and  circulating  pumps  which  are  placed  at  the 
back  of  the  condenser.  The  worm  and  worm-wheel, 
shown  at  W,  are  employed  to  move  the  engine  by 
hand  when  there  is  no  steam,  as  when  the  vessel  is 
in  port,  the  worm  obviously  being  thrown  out  of  gear 
with  the  wheel  when  not  in  use. 

Fig.  380  represents,  partly  in  section,  a  Compound 
Condensing  Marine  Engine,  for  an  ocean  going  steam- 


ship. The  main  valve  V  for  the  H.  P.  cylinder  is 
single  ported,  and  is  operated  by  a  link  motion  F 
that  is  used  for  reversing  only. 

A  Meyer's  cut-off  is  used,  the  two  cut-off  valves 
being  adjusted  to  vary  the  point  of  cut-off,  by  means 
of  a  right  and  left  hand  screw-thread.  To  permit  of 
the  operation  of  this  thread,  the  upper  end  of  the 
valve  rod  is  provided  with  a  hand  wheel  \V,  while  its 
lower  end  has  journal  bearing  in  the  foot  piece  R. 
The  rod  Z  for  operating  the  cut-off  valve  is  driven  by 
a  pin  in  a  crank  disc  D. 

The  low  pressure  valve  V  is  double  ported,  and  is 
driven  by  a  link  motion  G  that  is  used  for  reversing 
purposes  only.  Both  link  motions  are  shifted  by  a 
small  steam  cylinder,  whose  end  is  shown  at  X.  The 
piston-rod  of  this  small  cylinder  connects  at  its  outer 
end  with  a  screw  of  coarse  pitch,  so  that  when  steam 
is  admitted  to  the  cylinder,  and  the  hand  wheel  T  is 
revolved,  the  end  pressure  on  the  screw  will  (from 
the  coarse  pitch  of  the  latter)  cause  the  wheel  T  to 
continue  in  motion.  To  the  coarse  screw  is  fitted  a 
nut  upon  an  arm,  that  connects  to  the  tumbling 
shaft  that  shifts  both  link  motions  at  once.  When 
the  link  motion  has  been  shifted,  steam  is  shut  off 
from  the  small  cylinder.  The  speed  with  which  the 
shifting  is  effected  and  the  parts  come  to  rest,  is 
regulated  by  hand  pressure  on  the  wheel  T. 

Obviously  the  connection  between  the  coarse  screw 
and  the  piston-rod  is  such  as  to  permit  the  screw  to 
revolve  without  carrying  the  piston-rod  around  with 
it.  In  other  forms  of  steam  reversing  gears,  cataract 
cylinders  are  used,  the  general  principles  of  construc- 
tion being  such  as  were  explained  with  reference  to 
figs.  142  and  144. 

The  surface  condenser  is  shown  at  the  back  of  the 
engine,  the  air,  circulating,  and  bilge  pumps  being 
operated  by  the  respective  levers  B  B  and  B'  B', 
which  receive  motion  through  short  rods  C  C,  from 
the  cross-head.  Relief  or  snifter  valves  S.  S.  S.  S. 
are  provided  both  top  and  bottom  of  the  cylinders. 
To  enable  the  engine  to  be  turned  when  there  is  no 
steam,  the  crank-shaft  is  provided  with  a  worm- 
wheel  M,  operated  by  a  worm  on  the  rod  N,  at  whoi« 
upper  end  is  a  second  worm-wheel  and  worm,  the 
latter  being  operated  by  a  hand  ratchet  lever. 


280 


MODERN  STEAM  ENGINES. 


Fig.  379. 

llarins  Engine  for  Coasting  Vessels. 


THE  MA  RIM:  I:.\I;I.\E.  . 


2W 


W 


i<j.   3SO. 

Compound  Condensing  Marine  Engine. 


282 


MODERN  STEAM  ENGINES. 


Engine  with  the  '~Joif  Valve  Gear. 

Fig.  381  represents  an  engine  with  the  Joy  valve 
gear.  This  gear  is  used  to  vary  the  point  of  cut-oft', 
and  for  reversing  purposes.  Its  action  is  similar  to 
that  of  a  link  motion,  except  that  it  keeps  the  amount 
of  valve  lead  equal  for  all  points  of  cut-off,  whereas 
with  a  link  motion  the  valve  lead  varies,  as  the  link 
is  moved  from  full  gear  towards  mid  gear,  as  has 
been  fully  explained  witli  reference  to  link  motions. 

The  beam  L,  for  the  air  pump,  is  driven  from  the 
engine  cross-head  in  the  usual  manner.  The  valve 
motion  is  constructed  as  follows  :  A  lever  attached  to 
the  connecting-rod  at  one  end,  is  pivoted  at  the  other 
to  the  journal  or  pivot  of  the  box  J,  which  slides  in  a 
guide-way  in  the  drum  N.  The  lever  C  is  pivoted  to 
the  same  pin  or  journal  of  box  J,  and  is  supported  at 
its  other  end  by  the  rod  B,  which  is  pivoted  to  the 
pump  beam  L. 

The  rods  F  for  operating  the  valve-spindles  and 
therefore  the  valve,  are  attached  to  the  lever  C,  as 
shown.  When  the  slide-way  in  the  drum  N  stands 
horizontally  level,  the  parts  are  in  mid  gear,  and  the 
steam  port  opens  to  the  amount  of  the  valve  lead 
only,  while  when  the  slide-way  is  at  an  angle,  the 
travel  of  the  valve  is  increased,  the  direction  of  engine 
motion  being  governed  by  the  direction  of  inclination 
of  the  slide-way  in  N.  This  direction  is  adjusted  by 
means  of  the  handle  H,  by  which  the  drum  N  may 
be  rotated,  the  drum  being  secured  in  its  adjusted 
position  by  the  hand  screw  x.  The  principles  of  con- 
struction of  the  Joy  valve  gear,  may  be  more  fully 
explained  with  reference  to  fig.  382,  in  which  A  is  a 
lever  worked  at  one  end  by  the  connecting-rod,  and 
suspended  at  the  other  by  a  rod  B.  To  A  is  pivoted 
a  vibrating  lever  C,  pivoted  in  a  block  D,  and  work- 
ing at  its  right  hand  end  a  rod  F,  that  works  the 
valve  stem  or  valve  spindle  T.  The  segment  E  on 
which  block  D  slides,  is  pivoted  at  a  point  that  is,  in 
the  figure,  directly  behind,  and  in  line  with  the  pivot 
of  the  vibrating  lever  C. 

The  action  of  this  gear  may  be  divided  into  two 
elements,  first,  the  vibration  given  to  the  block  D,  by 


the  motion  of  the  connecting-rod,  which  gives  to  the 
valve  a  motion  sufficient  to  take  up  the  lap,  and  give 
to  the  port  the  required  amount  of  lead,  and  second,  a 
motion  derived  from  the  movement  of  block  D,  along 
the  arc  or  segment  E,  which  governs  the  amount  of 
opening  of  the  steam-port. 

The  position  of  segment  E  is  determined  by  the 
rod  G,  from  the  reversing  lever  H.  In  the  position 
in  which  E  is  shown  in  the  figure,  it  is  seen  that  as 
block  D  moves  along  it  to  the  left,  it  will  (from  the 
motion  of  D  alone,  and  independently  of  line  C)  pull 
rod  F,  and  therefore  the  slide  spindle  T,  downwards, 
thus  opening  the  head  end  port  for  the  admission. 
But  the  motion  of  vibrating  lever  C  has  already 
moved  the  valve  until  the  port  is  open  to  the  amount 
of  the  lead.  The  curve  of  segment  or  arc  E,  is  an  arc 
of  a  circle,  having  a  radius  equal  to  the  length  of  the 
rod  F,  so  that  if  lever  C  were  detached,  block  D 
might  be  moved  from  end  to  end  of  E  without 
imparting  any  motion  to  the  valve  spindle  T.  It 
follows,  therefore,  that  the  lever  A,  being  attached  at 
such  a  point  on  the  connecting-rod,  it  gives  to  the  rod 
F  an  amount  of  motion  only  sufficient  to  open  the 
port  to  the  amount  of  the  lap  and  lead  of  the  valve, 
therefore  when  E  is  set  (by  the  reversing  lever)  in 
mid-position,  its  arc  being  concentric  to  the  upper 
end  of  rod  F,  the  valve  will  open  to  the  amount  of 
the  lead  only. 

It  is  obvious,  that  as  the  amount  of  valve  motion 
necessary  to  take  up  the  lap,  and  give  the  desired 
amount  of  lead,  is  derived  from  the  connecting-rod, 
and  that  as  the  path  of  the  connecting-rod  remains 
the  same  for  all  points  of  cut-off,  therefore  the  valve 
lead  is  equal  for  all  points  of  cut-off.  The  amount 
of  lateral  motion  of  the  equalizing  lever  A,  at  its 
point  of  attachment  on  the  connecting-rod,  must  be 
as  a  minimum  equal  to  twice  the  valve  travel,  which 
would  give  no  lead,  the  increase  beyond  this,  reduces 
the  amount  of  angularity  of  the  segment  E,  required 
for  a  given  point  of  cut-off,  but  renders  it  necessary 
to  make  the  segment  longer,  in  order  to  obtain  a  given 
amount  of  port  opening.  The  pivot  of  lever  C  (in  the 
block  D),  must  move,  along  the  segment  E,  an  equal 
distance  on  each  side  of  a  vertical  line,  passing 
through  the  center  on  which  E  is  hung,  and  this  is 


nil-:  MMUM-:  I-:\<;ISE. 


283 


Fig.  381. 


Marine  Engine  With  Joy  Valve  Gear 


•284. 


MODERX  STEAM  EXG1XES. 


Fig.   382. 


285 


regulated  by  tlie  location  of  the  point  of  attachment 

of  the  vibrating  lever  C,  on  tlie  equalizing  lever  A. 
The  adjustment  nut  sliown  at  K.  is  for  lengthening 

in-  shortening   rod    B,  and  giving   more  lead    for  one 

port  tlmn  for  the  other,  when  it  is  desired  to  do  so, 

Tlie  ]Hiint  of  attaclinu'iit  of  vibrating  lever  V,  on  the 
equalizing  lever  A,  must  move  an  equal  distance 
aliove  and  below  the  pivot,  on  which  segment  E  is 
suspended,  and  so  long  as  this  is  tlie  case,  rod  A  may 
be  connected  from  any  point  that  has  a  motion  coinci- 
dent with  that  of  the  connecting-rod,  thus  in  fig.  381 
it  is  shown  attached  to  a  rod  B.  from  beam  L,  which 
is  also  employed  to  drive  the  air  pump. 


with  Bryce  Douglass'  Valve  Gear. 


Fig.  ."8;>  represents  a  Marine  Engine  fitted  with  a 
valve  motion,  designed  1>\-  Me.  Bryce  Douglass.  A 
short  beam  A  is  pivoted  at  its  center  to  tiie  cqnnect- 
ing-rod,  and  at  its  lower  end  to  a  link  attached  to  the 
engine  frame.  A  rod  T,  from  its  upper  end,  operates 
an  arm  on  the  shoe  S.  which  is  pivoted  at  it.s  center, 
so  as  to  vibrate  after  the  manner  of  a  link  motion. 

The  shoe  S  is  mounted  on  tlie  beam  L,  for  work- 
ing the  air  pump,  and  the  amount  of  vertical  motion 
given  to  the  shoe  by  the  air  pump  beam,  is  so 
regulated  as  to  move  the  rod  F,  and  therefore  the 
valve,  enough  to  take  up  the  lap,  and  also  give  to  tlie 
valve  the  required  amount  of  lead,  while  the  amount 
of  rocking  motion  of  S  on  its  center,  gives  the  port 
opening.  The  rod  F  lias  at  its  lower  end  a  block 
sliding  in  a  guide-way  in  shoe  S,  the  curve  of  this 
guide  way  being  an  arc  of  a  circle,  having  a  radius 
equal  to  the  length  of  the  rod  F,  so  that  if  the  shoe  S 
is  stationary,  and  in  mid-position,  the  lower  end  of 
F  can  be  moved  from  end  to  end  of  S,  without  im- 
parting any  motion  to  F,  and  it  follows  therefore, 
that  at  mid-gear  (S  then  being  horizontal)  the  valve 
opens  to  the  amount  of  the  lead  only,  and  the  lead 
is  equal  for  all  points  of  cut-off. 

Reversing  is  effected  by  moving  the  block  on  the 
lower  end  of  F,  to  one  on  the  other  side  of  the  pivoted 
center  of  S,  while  the  point  of  cut-off  is  determined 


by  the  distance  the  block  on  the  foot  of  F  stands 
from  the  pivoted  point  or  center  of  S,  it  being  obvious, 
that  tlie  nearer  this  block  is  to  the  end  of  S,  the 
.ter  the  valve  travel,  and  the  later  in  the  stroke, 
the  point  of  cut-oil' will  occur. 

IJnd  F  is  shifted  for  varying  the  point  of  cut-off,  or 
for  reversing  the  direction  of  engine  motion  as  follows: 

At  I!,  is  a  segmental  rack,  connected  by  rod  to  F, 
as  shown.  The  pinion  for  this  rack  is  on  the  same 
shaft  as  wheel  W,  this  pinion  is  driven  from  the  steam 
cylinder  (.'.  beneath  which  is  a  cataract  cylinder  I) 
for  regulating  the  speed  at  which  the  rack  shall  be 
moved,  and  enabling  the  engineer  to  stop  the  motion 
at  the  desired  point. 

For  moving  the  engine  without  the  aid  of  steam, 
provision  is  made  as  follows:  First  by  a  worm-wheel 
and  worm,  the  latter  being  operated  by  a  ratchet  lever 
as  shown  ;  and  secondly,  by  a  train  of  gear  wheels  con- 
necting  the  lower  end  of  the  worm  shaft  with  the  wheel  e, 
ii\  .vhose  face  are  slots  for  tlie  reception  of  a  hand  lever. 

The  main  difference  in  the  act  ion  of  this  valve  motion 
in  comparison  with  the  Joy  valve  motion  is,  that  here 
the  block  at  the  foot  of  rod  F,  in  the  shoe  S,  has  an 
amount  of  motion  which  varies  with  the  point  of  cut- 
off, and  which  for  all  reduced  points  of  cut-off  is  less 
I  than  is  the  case  with  the  Joy  gear,  and  the  wear  will 
therefore  be  more  uneven  and  greater.  In  the  Joy 
gear,  the  length  of  motion  of  the  sliding  block  along 
the  segment  is  the  same  for  all  points  of  cut-off,  hence, 
not  only  is  the  wear  equal,  but  the  lost  motion  may 
be  taken  up,  whereas,  when  the  wear  is  unequal  at 
different  places  in  the  same  bar  or  guide,  the  fit  must, 
in  taking  up  the  lost  motion,  be  made  to  suit  the 
least  worn  part  or  spot. 


Examples  of  Triple  Expansion 
Engines. 

The  valve  gears  and  link  motions  of  triple  expan- 
sion marine  engines  are  of  the  same  forms  and  in- 
volve precisely  the  same  principles  of  construction  as 
the  valve  gears  and  link  motions  of  compound  and 
other  engines,  the  main  difference  being  that  as  three 


286 


MUDKKX  STEAM  EXUIXES. 


Marine  Engine,  with  Bryce  Douglass's  Valve  Sear. 


THE  MARINE  EXGIXE. 


287 


sets  of  gear  are  required  instead  of  two,  the  parts  are 
more  crowded  and  less  easy  of  access. 

Examples  of  triple  expansion  engines  are  given  as 
follows : 

Figs.  383a,  3836  and  383c  represent  the  engines  of 
the  S.  S.  Mariposa,  these  figures  being  taken  from 
"  Engineering."  The  diameters  of  the  cylinders  are 
11  inches,  18  inches  and  25  inches  respectively,  with 
a  stroke  of  18  inches. 

The  high-pressure  and  intermediate  pressure  cyl- 
inders are  fitted  with  piston  valves,  while  the  low 
pressure  cylinder  has  a  doulile  ported  Hat  valve. 

An  especial  feature  of  this  vn.^ine  is  its  valve  gear, 
which  is  constructed  under  Morton's  patent. 

In  this  valve  gear  the  port  openings  in  either  for- 
ward or  backward  gear  are  equal  for  equal  move- 
ments of  the  main  piston  from  either  end  of  its  stroke, 
while  the  valve  lead  is  maintained  constant  at  all 
points  of  cut-off. 

The  construction  of  this  valve  gear  is  shown  in 
Fig.  383c.  The  radiating  crank  P  is  carried  in  a 
projection  (which  may  be  a  block)  fitted  to  the  con- 
necting rod.  The  crank  P  is  so  proportioned  that  its 
pin  A  radiates  equally  across  the  center  line  of  the 
connecting  rod,  and  remains  practically  in  relation 
to  the  center  line  of  the  connecting  rod  during  a  rev- 
olution of  the  engine. 

Movement  is  imparted  to  the  radiating  crank  pin 
A  from  the  piston  through  the  link  B,  which  is  at- 
tached to  the  crosshead  slide  at  D,  which  actuates 
the  prolonged  end  of  the  "lead  lever,"  or  valve 
lever  F. 

Thus  it  will  be  seen  that  the  travel  or  movement 
imparted  to  the  radiating  crank  pin  A  B  is  in  a  rela- 
tively contrary  direction  to  that  in  which  the  piston 
may  be  moving,  and  of  the  amount  required  to  cor- 
rect the  error  due  to  the  angularity  of  the  connecting 
rod,  but  also  to  compensate  and  correct  the  angular- 
ity of  the  lead  lever  or  valve  lever  F  by  one  and  the 
same  movement,  so  that  the  fulcrum  center  G  of  the 
lever  F,  (which  moves  on  an  arc  described  by  the 
link  C,  vibrating  from  the  fixed  center  K,)  has  a  mo- 
tion imparted  to  it  in  time  with  that  of  the  piston. 
The  overhung  end  G  N  of  the  valve  lever  F  is  so  pro- 
portioned as  to  travel  the  amount  of  the  lap  +  the 


lead  of  the  valve,  and  when  the  engine  crank  is  on 
either  the  top  or  bottom  center,  and  the  valve  motion 
in  such  gear,  the  center  line  of  the  adjustable  link  H 
lies  through  the  center  of  the  valve  spindle  and  par- 
allel to  the  center  line  of  link  C  and  that  of  the  con- 
necting rod. 

The  expansion  quadrant  I  is  made  in  the  form  of 
the  letter  T  inverted,  the  slotted  head  is  curved  to  the 
radius  of  the  adjustable  link  H,  and  fitted  with  a 
steel  die  block  J,  to  which  the  link  H  is  connected, 
and  these  two  pieces  are  again  connected  to  the  le- 
vers on  the  reversing  shaft  by  the  usual  form  of  drag 
link.  It  will  be  understood  that  the  position  of  the 
die  block  J  in  the  quadrant  regulates  the  degree  of 
the  expansion  and  the  direction  of  engine  rotation 
after  the  manner  of  a  "Gooches"  Link;  since,  when 
the  valve  gear  is  in  mid  gear  the  link  block  J  may 
be  moved  from  end  to  end  of  the  link  I  without  its 
moving  the  valve,  and  hence  without  altering  the 
amount  of  valve  lead. 

The  triple  expansion  engines  of  the  steam  yacht 
Mira,  built  by  Messrs.  David  J.  Dunlop  and  Co.,  of 
Port  Glasgow,  North  Britain,  are  shown  in  figs.  383d 
and  383e. 

These  engines  are  of  500  horse-power  when  the 
boiler  has  natural  draught,  and  800  when  under 
forced  draught  The  diameters  of  the  cylinders  are, 
high-pressure  cylinder  14  inches,  intermediate  cylin- 
der 22  inches,  and  low-pressure  cylinder  36  inches ; 
the  stroke  being  24  inches. 

Referring  to  the  figures  :  H.  P.  is  the  high-pressure, 
I.  P.  the  intermediate,  and  L.  P.  the  low-pressure 
cylinder,  which  are  supported  at  the  back  by  columns 
X  on  the  condenser  W  (Y  being  the  exhaust  pipe 
from  the  low-pressure  cylinder  to  the  condenser),  and 
in  front  by  steel  column?. 

The  construction  of  the  valve  gear  is  as  follows : 
The  high-pressure  cylinder  H.  P.  has  a  piston-valve 
shown  at  V,  which  is  worked  direct  from  an  ordinary 
Stevenson  Link  Motion,  whose  rods  are  shown  at  g, 
g,  fig.  383e,  which  shows  the  link  motion  for  the  high- 
pressure  cylinder.  The  rod  A  connects  at  B  to  a  die 
movable  in  a  slide-way  which  is  fast  on  the  arm  C 
of  the  reversing  shaft  D  by  means  of  a  screw,  so  that 
the  point  of  suspension  of  the  link  can  be  altered,  the 


288 


MO DEUX  STEAM  E.\GL\ES. 


mi:  VI///Y/;  few'/**        UNIVERSITY 


. 


Fig.  3836. 


290 


MODERN  STEAM  ENGINES. 


Fig.  383.C 


Till-:  MA  HIM-:   /••Y'./.y.V. 


291 


Triple  2-jar.:i:r.  Engines  of  Steam  7acht  liira. 


MUDEIL\  XTEA.M  EX 


> 


Fig.  383e. 

Triple  Expansion  Engine  of  Steam  Yacht  Mira. 


MARL\  / 


293 


Fig.  383/. 


€c.S*  LIEM 
'ME 
[VERSITY, 
OF 
f. 


294 


MODERN  STEAM  ENGINES. 


Fig.  WSg. 


THE  J/.-lA'AYA;  A\\Y,7.VA;. 


2U5 


296 


MODERN  STEAM  ENGINES. 


effect  being  that  by  operating  the  screws  to  move  the 
die  up  the  slideway  B  the  link  is  further  over  towards 
full  gear,  which  increases  the  stroke  of  the  valve  and 
prolongs  the  point  of  cut-off. 

A  similar  device  is  employed  for  the  valve  gear  of 
the  intermediate  and  low-pressure  cylinders. 
The  object  of  this  arrangement  is  as  follows  : 
The  reversing  shaft  D  is  operated    by  the  hand- 
wheel   D,  all  three  of  the  reversing  gears  being  of 
course  operated  simultaneously,  and  by  the  employ- 
ment of  the  slideways  B  B'  B"  each  cylinder  may  be 


At  K  are  the  non  return  or  check  valves,  which  are 
employed  to  prevent  the  sea  water  from  flowing  or 
siphoning  into  the  bilge  in  cases  where  the  engine  is 
stopped  and  the  cock  L  is  open.  At  r  r  are  the 
plungers  for  the  circulating  pumps,  while  </  J  are 
air-chambers  for  the  bilge  and  circulating  pumps 
respectively. 

The  gear  for  turning  the  engine  around  by  hand 
is  shown  in  fig.  3S3r/,  W  being  the  worm  for  the 
worm-wheel  ?(/,  the  worm  being  operated  by  hand 
bv  means  ot'  the  ratchet  lever  L 


given  a  different  degree  of  expansion ;  or,  in  other 
words,  the  point  of  cut-off  for  each  valve  may  be 
regulated  at  will  without  affecting  the  points  of  cut- 
off of  either  of  the  other  valves. 

The  pumps  are  operated  as  follows : 

The  levers  or  beams  E  E'  are  worked  from  the 
cross-head  of  the  intermediate  cylinders  and  connect 
by  short  rods  to  the  gudgeon  or  shaft  a,  the  rods  c  c 
being  for  the  air  pumps,  whose  cylinders  are  shown 
at  F  F  in  fig.  383d  The  plungers  e  e  are  for  the  bilge 
pumps  G ;  the  bilge  pipe  connecting  at  H  and  L  is 
the  cock  for  cutting  off  the  flow  from  the  bilge  to  the 
bilge  pumps  whenever  it  may  be  found  necessary. 


383t. 

Figs.  383/,  383#,  383A  and  383t,  which  are  taken 
from  "  Engineering,"  represent  the  triple  expansion 
engines  of  the  steamship  Meteor,  which  is  provided 
with  a  steam  reversing  gear  at  a,  the  link  motion  and 
valve  gear  being  of  the  ordinary  type. 

A  test  of  these  engines  is  given  as  follows : 

RESEARCH     COMMITTEE     ON     MARINE     ENGINE     TRIALS. 
REPORT   UPON   TRIALS   OF   THE   S.    S.    METEOR. 

From  a  paper  read  be/ore  the  Institution  of  Mechanical 
Engineers.     By  Professor  Alexander  B.    W.  Kennedy, 
F.  R.  S.,  Chairman. 
The  S.   S.  Meteor  is  a  steamer  belonging  to  the 


TIU-:  .I/.IA'/.Y/:  i:\tn\E. 


207 


298 


MODERN  STEAM  ENGINES. 


London  and  Edinburgh  Shipping  Company,  and  per- 
mission to  test  her  engines  was  most  kindly  given  to 
the  Committee  by  Mr.  Thomas  Aitken,  the  manager 
of  the  company,  who  with  his  staff  and  all  the  of- 
ficials on  board  the  ship  have  done  their  utmost  to 
facilitate  the  work  of  the  trial. 

The  Meteor  is  a  vessel  of  261  ft.  in  length  between 
perpendiculars,  32.1  ft.  in  breadth,  and  19.3  in  depth 
moulded.  Her  registered  tonnage  is  692  and  gross 
tonnage  1223,  under  deck  958  tons. 

Her  displacement  on  the  day  of  the  trial,  when  the 
mean  draught  was  15  ft.  li  in.,  was  2090  tons. 

Engines. — She  is  fitted  with  triple-expansion 
engines  made  by  Messrs.  J.  and  G.  Thompson,  of 
Clydebank,  Glasgow.  The  high-pressure  cylinder, 
originally  29  in.  in  diameter,  lias  been  rebored  to 
291  in.  in  diameter ;  the  intermediate  cylinder  is  44  in. 
in  diameter,  and  the  low  pressure  70  in. ;  the  stroke 
of  all  three  cylinders  is  4  feet.  The  piston-rods  are 
all  7  in.  in  diameter ;  the  tail  rod  of  the  high -pressure 
cylinder  is  4.45  in.  in  diameter,  and  the  tail  rods  of  the 
other  two  cylinders  4.37  in.  in  diameter.  These  rods 
have  been  measured,  and  the  stroke  of  the  engine  has 
also  been  measured,  and  found  to  be  exactly  47.94  in. 
instead  of  48  in.  There  has  been  no  opportunity  of 
measuring  the  diameter  of  the  cylinders. 

The  three  cranks  are  spaced  at  equal  distances 
apart  and  follow  in  the  order — high,  intermediate, 
low. 

The  cylinders  are  made  with  separate  liners,  and 
are  jacketted  at  the  sides  but  not  at  the  ends.  The 
net  length  of  the  jacketted  space  is  about  4  ft.  Live 
steam  is  admitted  separately  to  each  of  the  jackets, 
each  having  its  own  reducing  valve.  The  jackets  are 
drained  through  pockets  provided  with  gauge  glasses, 
and  during  the  trial  water  was  always  kept  visible  in 
these  gauges. 

The  clearances  of  the  high-pressure,  intermediate, 
and  low-pressure  cylinders  are  given  by  the  makers 
as  12.4,  9.3,  and  8.02  per  cent,  respectively. 

Each  cylinder  is  provided  with  a  piston  valve  or 
valves,  single  for  the  high-pressure  cylinder  and 
double  for  each  of  the  others. 

The  valve  gear  is  the  ordinary  link  motion,  and 
during  the  trial  the  high-pressure  motion  was  linked 


up  as  much  as  possible,  giving  a  nominal  cut-off  of 
26  in.;  the  intermediate  and  low-pressure  motions 
were  not  linked  up.  The  valve  gear  was  left  untouched 
during  the  whole  of  the  trial.  The  surface  condenser 
has  3200  square  ft.  of  condensing  surface.  The 
screw  propeller  is  four-bladed,  having  a  diameter  of 
14'  10",  and  a  mean  pitch  of  23  ft.  The  actual  area 
of  the  blades  is  78  square  ft.,  and  the  projected  area  57. 

6  square  ft.     The  engines  had   been   overhauled  last 
at  the  annual  survey  which  took  place  March  1  to  14, 
1888. 

Boilers. — The  boilers  are  two  in  number,  each 
double-ended,  the  total  number  of  furnaces  being 
twelve.  They  are  of  steel,  with  Fox's  corrugated 
flues,  and  have  a  diameter  of  13  feet  6  inches,  and  a 
length  of  16  feet.  The  total  grate  surface  in  the  trial 
was  208  square  feet,  and  the  total  tube  surface  5760 
square  feet,  the  ratio  between  the  two  being  1  to  27.7. 
The  total  heating  surface  is  6648  square  feet,  or 
thirty-two  times  the  grate  surface.  The  mean  diam- 
eter of  the  flues  is  3  feet  3  inches.  The  firebars  are 
of  ordinary  description,  3  feet  long,  1  inch  broad  at 
top  in  body,  and  about  1J  inches  at  the  ends,  the  air 
spaces  being  thus  about  J  inch  wide. 

There  are  twenty-five  bars  in  the  width  of  each 
furnace,  and  therefore  fifty  bars  in  each  grate.  There 
is  no  air  admission  at  the  bridge  or  anywhere  except 
from  the  front  and  from  below  the  bars.  The  tubes 
are  2*  inches  external  diameter  and  6  feet  41  inches 
long.  The  furnaces  and  tubes  open  out  into  a  com- 
mon combustion  chamber.  The  two  boilers  have 
one  chimney  in  common,  whose  internal  diameter  is 

7  feet  3  inches;  the  external  diameter  of  the  outer 
chimney  is  8  feet   3J    inches.     The  chimney  has   a 
total  height  of  61  feet  above  the  centre  of  the  lowest 
furnace.     The  total  weight  of  the  engines  and  boilers, 
including  water  in  condenser,  pipes  and  boilers,  and 
also  spare  gear,  is  390}  tons. 

Object  of  Trial. — The  object  of  the  trial  was  to  meas- 
ure the  coal,  water  and  indicated  horse-power  as  ac- 
curately as  possible  and  over  as  long  a  period  as  pos- 
sible. 

Goal  Measurement. — For  weighing  the  coal  a  spring 
balance  was  used  in  each  stokehole.  From  the 
spring  balance  was  suspended  a  large  basket  holding 


THK 


J-:.\<;I\K. 


299 


about  MO  pounds  of  coal.  This,  being  filled,  was 
hoisted  liy  tackle,  its  weight  noted,  and  tin-  coal  then 
thrown  upon  the  stokehole  floor.  Aliout  six  haskrts 
were  tilled  and  emptied  as  rapidly  as  po>-ihle  one 
:•  the  other,  first  on  the  starboard  side  and  then 
on  the  port  Mile  of  the  stokehole  floor,  giving  thus 
t\vi>  weighed  heaps  ofahoiit  SOO  pound-  of  coal  each. 
The  time  at  which  each  heap  was  finished  i  that  is, com- 
pletely put  oil  the  tires  was  noted,  and  no  more  coal 
was  weighed  out  until  the  floor  was  clear.  A  contin- 
uous record  of  coal  thrown  on  the  fires  was  thus  kept, 
which  plots  out  into  the  line  of  coal  consumption 
shown  upon  the  diagram,  No.  1,  Fig.  •!>•>/'.  The  fires 
were  not  cleaned  during  the  run.  hut  the  cleaning 
commenced  when  the  trial  was  over,  and  the  ashes 
and  clinkers  were  weighed  hefore  being  thrown  over- 
board. The  coal  was  Scotch,  from  the  Sliawlield  pit 
in  the  \Vishaw  district,  its  price  at  Leith  being  7.--.  C«l. 
per  ton.  It  has  heen  aiialy/.ed  and  its  salorimetric 
value  determined  by  Mr.  ('.  .1.  Wilson,  F.  ('.  S..  of 
University  College,  Loiulon,  with  the  following  re- 
sults: 


Carbon       .... 

Hydrogen        - 

Water 

Ash      - 

t-n,  Sulphur  and  Oxygen    - 


/'•/•  frii/. 

To  :;i 

1  <^ 

10.68 

3.40 

KM;: 

100.00 


36  figures  are  the  mean  of  two  almost  identical 
analyses.  Reducing  the  hydrogen  to  the  correspond- 
ing value  of  carbon,  eacii  pound  of  coal,  not  allowing 
of  course  for  the  bad  lumps  which  formed  the  greater 
part  of  the  clinker,  is  thus  equivalent  to  0.878  pounds 
of  carbon,  and  its  calorific  value  may  be  taken  as 
12,790  thermal  units. 

/  net  <i  ues. — The  temperature  of  the  gases  pass- 
ing up  the  chimney  was  observed  at  intervals  through- 
out the  trial,  the  thermometer  being  placed  at  the 
level  of  the  upper  deck,  or  about  12  feet  above  the 
top  of  the  boiler.  The  thermometer  was  long  enough 
to  reach  over  two  feet  into  the  chimney.  It  was  a 
mercury  thermometer,  the  space  above  the  mercury 
being  filled  with  compressed  nitrogen,  so  as  to  enable 


it  to  give  readings  far  above  the  ordinary  boiling 
point  of  mercury.  Samples  of  the  gases  from  the 
chimney  were  collected  during  the  trial,  and  placed 
iu  sealed  bottles  over  mercury.  Unfortunately,  how- 
ever, all  the  samples  taken  except  one  were  spoilt 
before  they  reached  the  laboratory  for  aualvsis.  The 
analysis  of  this  sample  has  been  made  by  Mr.  C.  J. 
Wilson,  and  is  given  later  on. 

The  chimney  draught  was  measured  by  a  U  gnuge 
at  the  place  where  the  fum  -  were  collected. 

\Vntfi-  M/-ii.iiii;-,n<'iit. — The  feed  water  was 
measured  on  its  way  from  the  hot-well  to  the  feed 
pump,  the  hitter  being  a  Worthington  pump  entirelv 
separate  from  the  engine.  A  4  in.  pipe  was  connected 
with  the  hot-well  and  terminated  in  a  4  in.  two-way 
cock,  by  means  of  which  the  discharge  could  be 
turned  into  either  one  or  two  measuring  tanks.  At 
the  bottom  these  tanks  were  connected  to  another  4 
in.  two-way  cock,  through  which  the  feed  pump 
could  be  made  to  draw  from  either  of  them. 

The  tanks  were  so  tilted  that  one  corner  was  lower, 
and  another  corner  higher  than  all  the  rest,  so  as  to 
render  their  filling  and  emptying  more  certain. 
They  were  fitted  with  glass  water  gauges  and  with 
relief  pipes.  The  method  of  operation  was  as  follows : 
The  hot-well  discharge — which  contained  the  con- 
densed steam  passing  through  the  cylinders,  the 
jacket  condensation,  and  also  the  steam  used  for 
heating  the  feed  water,  as  well  as  the  other  quantities 
mentioned  in  the  next  paragraph — was  allowed 
always  to  run  into  one  or  the  other  tank,  and  filled 
each  one  up  in  turn  in  about  3J  minutes.  By  means 
of  the  lower  cock  the  feed  pump  was  put  into  connec- 
tion with  the  tank  into  which  the  hot-well  was  not 
|  discharging  and  emptied  in  about  2}  minutes.  For 
each  tankful,  there  was  therefore  about  one  spare 
minute  in  which  to  insure  its  complete  emptiness  or 
fullness  and  to  note  the  temperatures,  etc. 

During  this  time  the  feed  pump  bad  to  be  stopped, 
being  started  again  directly  the  next  tank  was  full. 

After  the  trial  the  tanks  were  re-erected  with  all 
their  connections  at  University  College,  London,  and 
water  carefully  weighed  into  them.  It  was  found 
that  one  held  1808  Ibs.  and  the  other  1785  Ibs.  of 
water  at  62  deg.  Fahr.,  and  also  that  the  probable 


300 


MODERN  STEAM   ENGINES. 


error  of  the  filling  and  emptying  as  carried  out  on 
the  trial  was  not  more  than  2  pounds  in  each  tank, 
and  was  equally  likely  to  be  plus  or  minus. 

It  seems,  therefore,  that  the  method  of  water 
measurement  used,  although  very  laborious,  must 
have  given  very  closely  accurate  results.  A  more 
elaborate  system  with  storage  tanks,  which  was 
preferred  by  the  Committee,  could  not  he  carried  out 
for  want  of  room  on  the  vessel.  The  temperature  of 
each  tank  was  taken,  so  that  a  very  good  average  of 
the  feed  water  temperature  was  obtained. 

The  steam  made  by  the  boilers,  corresponding  with 
the  measured  weight  of  the  water,  all  went  to  the 
main  engine,  except  the  small  quantity  required  to 
drive  the  Worthington  pump,  which  ma}'  be  fairly 
considered  comparable  with  the  quantity  required  for 
the  feed  pump  of  an  ordinary  engine.  The  circu- 
lating pump,  the  dynamo  engine,  the  winch  en -lines, 
the  steering  engines,  etc.,  were  all  worked  from  a 
donkey  boiler,  which  was  specially  kept  going  for 
that  purpose.  The  exhaust  from  the  circulating- 
pump  engine  and  also  that  from  the  dynamo  engine 
were  both  taken  into  the  condenser,  and  therefore 
were  measured  through  the  feed  tank  on  their  way  to 
the  boiler  again.  These  additions  to  the  ordinary 
air  pump  discharge  more  than  made  up  for  the 
various  losses  of  steam  through  the  engine,  so  that 
from  time  to  time  part  of  the  hot-well  discharge  had 
to  be  thrown  away,  and  not  taken  back  to  the  boiler. 
The  whole  of  the  pipe  connections  between  the 
boilers  and  engines,  which  were  of  very  great  com- 
plexity, were  carefully  examined  before  the  trial  to 
make  sure  that  no  unintended  communication 
existed. 

Power  Measurement. — Indicator  diagrams  were  taken 
at  half-hourly  intervals  throughout  the  whole  trial. 
Six  Crosby  indicators  were  used,  one  on  each  end  of 
each  cylinder.  The  connections  in  all  cases  were 
through  only  a  few  inches  of  large  pipe,  having  in  no 
case  more  than  one  bend. 

The  revolutions  were  noted  half-hourly  on  the 
counter,  all  the  gauges  being  read  at  the  same  time. 

General  Conditions. — The  general  conditions  as  to 
speed,  power,  steam  pressure,  frequency  of  stoking, 
and  so  on,  were  all  those  of  ordinary  working  on  a 


southward  journey,  and  were  fixed  beforehand  by  the 
chief  engineer. 

Results. — The  results  are  shown  graphically  in 
Fig.  383j,  Nos.  1  and  2,  and  their  principal  points  are 
the  following: 

Duration  of  Trial. — The  trial,  which  was  made  on  a 
voyage  from  Leith  to  London,  commenced  at  1.30 
A.  M.  on  Sunday,  June  24th,  and  ended  for  the 
engines  at  6.36  p.  M.,  and  for  the  boiler  at  6.39  p.  M. 
upon  the  same  day.  Its  duration  was  therefore  17 
hours  6  minutes  for  the  engines  and  17  hours  9  min- 
utes for  the  boilers.  This  small  difference  of  three 
minutes  arises  from  the  fact  that  the  signal  for  end- 
ing the  engine  trial — that  is,  for  taking  the  last  read- 
ing of  the  counter — was  given  three  minutes  before 
the  water  in  the  boiler  gauge  glass  reached  the  level 
from  which  it  had  started.  The  weather  was  fair 
throughout. 

Fuel. — The  coal  used  in  the  after  stokehole  was 
16,675  pounds  upon  the  starboard  side  and  Ki.S.ll 
pounds  upon  the  port  side.  In  the  forward  stoke- 
hole these  amounts  were  respectively  18,i'42  pounds 
and  16,945  pounds.  The  starboard  boiler,  therefore, 
used  34,917  pounds  and  the  port  boiler  33,776  pounds 
of  fuel.  The  total  quantity  was  68,693  pounds,  or 
4005  pounds  per  hour.  At  the  end  of  the  trial  it 
was  found  on  cleaning  the  fires  that  the  ash  amounted 
to  1671  pounds,  and  the  clinker  to  2806  pounds  in 
addition.  The  ash  was  therefore  2.43  per  cent,  of  the 
total  fuel,  the  clinker  4.08  per  cent,  of  the  total  fuel, 
and  the  two  together  6.51  per  cent,  of  the  total  fuel. 

The  mean  temperature  of  the  escaping  gases  de- 
duced from  thirty-eight  observations  was  791  degrees 
Fahrenheit.  The  chimney  draught  was  constantly 
about  -fs  inches  of  water.  The  sample  of  furnace 
gases  which  was  brought  successfully  to  analysis  gave 
the  following  results  by  volume: 


Carbonic  Acid 
Oxide 
Oxygen 
Nitrogen 


Per  cent. 

-       1L>.  f> 

0.8 

5.4 

81.2 


This  sample  was  collected  at  11.30  A.  M.  under 


mi.  M.IKIM-;  I-:.\<;L\]-:. 


301 


normal  conditions  of  working.  During  tin-  greater 
part  of  the  trial  the  ihvs  \vi-rc  worked  very  thick, 
indeed  as  thick  as  possible,  and  they  \vcrc  so  at  the 
end  of  the  trial.  As  already  mentioned,  they  were 
not  cleaned  during  the  trial.  Very  much  smoke  was 
always  emitted  alter  stoking;  liiit  while  no  stoking 
was  actually  going  on  there  was  not  much  smoke. 
The  times  of  stoking  were  noted  frequently,  and  on 
the  average  it  was  found  that  stoking  occurred  in 
each  stokehole  ahoiit  every  L'1  minutes,  all  the  fires 
being  stokeil  one  alter  the  other  as  quickly  as  pos- 
sible. 

The  mean  temperature  of  the  fn-d 
water,  which  was  heated  hefore  leaving  the  hot  Well 
by  :iu  apparatus  devised  hy  Mr.  Clephane.  the  chief 
engineer  of  the  ship,  was  1(1.",. 1  degrees  Fahrenheit.  It 
was  very  fairly  constant  between  ]l>D  degree:-  and  170 
degrees  during  the  whole  trial.  At  this  temperature 
the  uniounls  of  water  contained  hy  the  two  measur- 
ing tanks  are  1771  pounds  and  17111  pounds  respec- 
tively, these  figures  heing  futuid  hy  calculation  from 
those  already  given.  During  the  trial  the  larger  tank 
was  tilled  14")  times,  and  the  smaller  141!  times.  The 
total  quantity  of  water  used  was  therefore  512,150 
pounds,  or  •_".!. Mil)  pounds  per  hour. 

•V-,/.—  The  counter  read  1,439,<5(>8  at  1.30  A.  M. 
when  the  trial  commenced,  and  1,513,318  at  6.36 
p.  M.  when  the  trial  ended.  The  total  number  of 
revolutions  made  hy  the  engines  was  therefore  73,650, 
the  time  being  17  hours  fi-minutes,  which  gives  the 
average  rate  of  71. 7S  revolutions  per  minute.  The 
maximum  number  of  revolutions  per  minute  for  any 
half-hour  was  7:2.4.  and  the  minimum  70.9. 

Pressures,  etc. — The  mean  barometric  pressure  dur- 
ing the  trial  was  .'J0.34  inches  of  mercury,  or  say  14.9 
pounds  per  square  inch.  The  mean  boiler  pressure 
was  145.2  pounds  per  square  inch.  The  other  press- 
ures were  as  follows : 

1'oinnh  per 
tqnnri'  inch. 

High-pressure  Jacket  ...      131.0 

Intermediate         "  •  77.5 

Low-pressure        "  -  -  56.8 

First  Receiver  -  -  36.5 

Second     "  ...          6.2 

All  these  pressures  are  given  above  the  atmospheric 


ire.        They    were    observed    every    half-hour 

throughout  the  trial.  The  gauge  for  the  boiler  pi> 
lire  was  checked  by  a  standard  gauge;  the  other 
gauges  were  not  checked,  and  their  reading  must 
therefore  be  taken  as  approximate  only.  The  average 
pressure  during  admission  to  the  high-pressure  cylin- 
der (from  measurements  of  diagrams)  was  i:>4.4 
pounds  per  square  inch.  The  actual  initial  pressure 
(or  pressure  just  at  the  commencement  of  the.  stroke) 
was  practically  the  same  as  this  in  the  top  diagrams, 
and  (i  or  7  pounds  higher  in  the  bottom  diagrams. 
The  difference  between  the  average  admission  press- 
ure and  the  boiler  pressure  was  thus  (assuming  the 
gauge  to  be  correct)  10.8  pounds  per  square  inch. 
The  mean  reading  of  the  vacuum  gauge  was  24.78  of 
mercury,  or  1:M7  pounds  per  square  inch  below  the 
atmosphere.  The  mean  vacuum  in  the  low-pressure 
cylinder  <  obtained  by  detail  measurement  of  all  the 
diagrams  i  was  11. (J  pounds  per  square  inch  below  the 
atmosphere.  The  absolute  back-pressure  was  there- 
fore 2.73  pounds  in  the  condenser,  assuming  the 
gauge  to  be  correct,  and  3.3  pounds  in  the  cylinder. 

I'oii-fi; — The  following  are  the  mean  effective 
pressures  in  the  different  cylinders  in  pounds  per 
square  inch  : 


High-pressure  -    - 

Intermediate     -     - 
Low-pressure    -    - 


Top. 

60.10  - 

20.47  - 

12.22  - 


Bottom. 
56.82    - 

18.54  - 

12.55  - 


Mean. 

-  58.46 

-  19.50 

-  12.38 


These    pressures    correspond    with    the     following 
indicated  horse-power : 

High-pressure  cylinder     ....... 

Intermediate  ........ 

Low-pressure        "      ........ 


Total  indicated  horse-power 


662 
507 
825 

1994 


These  figures  are  the  average  from  thirty-four  sets 
of  diagrams,  six  diagrams  in  each  set.  The  max- 
imum indicated  horse-power  given  hy  any  one  set 
was  2086,  taken  at  5.15  A.  M.  with  72.1  revolutions 
per  minute  and  147  Ihs.  boiler  pressure.  The  min- 
imum indicated  horse-power  given  by  any  one  set  of 
diagrams  was  1890,  taken  at  12.45  p.  M.  with  70.9 
revolutions  per  minute  and  140  Ibs.  boiler  pressure. 


302 


MOD  Kit  X  STEAM 


Each  sei  of  diagrams  was  worked  out  for  the  revolu- 
tions per  minute  corresponding  with  the  counter  read- 
ings for  the  half  hour  in  which  that  set  was  taken. 
One  set  of  diagrams — the  nearest  to  the  mean — is 
given  in  Fig.  383j,  Nos.  5  to  7. 

Boiler  Efficiencies. — The  rate  of  combustion  in  the 
furnaces  was  19.25  Ibs.  of  fuel  per  square  foot  of 
grate  surface  per  hour,  or  0.602  Ibs.  per  square  foot 
of  total  heating  surface  per  hour.  The  evaporation 
was  at  the  rate  of  7.46  Ibs.  of  water  per  pound  of 
fuel  put  on  the  fire,  including  clinker.  This  water, 
being  supplied  at  a,  temperature  of  163  degrees  Fah- 
renheit, and  evaporated  at  a  temperature  of  363 
degrees,  must  have  received  heat  at  the  rate  of  1062 

o 

thermal  units  per  pound.  Eacli  pound  of  it  was 
therefore  equivalent  to  1.10  Ibs.  evaporated  from  and 
at  212  degrees.  The  actual  evaporation  reduced  to 
this  standard  was  therefore  8.21  Ibs.  of  water  per 
pound  of  coal,  or  about  9.62  Ibs.  per  pound  of  carbon 
value  in  fuel,  allowing  for  clinker.  The  equivalent 
amount  of  heat  utilized  per  pound  of  coal  was  7922 
thermal  units,  or  say  62  per  cent,  of  the  whole  calor- 
ific value  of  the  coal,  which  percentage  therefore 
represents  the  actual  boiler  efficiency.  The  total 
nominal  calorific  value  of  the  fuel  burnt  per  minute 
was  853,900  thermal  units.  Although  it  cannot  be 
assumed  that  the  analysis  of  furnace  gas  already 
given  was  a  fair  average,  it  has  been  thought  worth 
while  to  work  it  out.  It  appears  from  it  that  the 
weight  of  air  per  pound  of  carbon  was  about  22.0 
Ibs.,  and  per  pound  of  coal  about  15.5  Ibs.  The  loss 
of  heat  in  raising  the  temperature  of  the  furnace 
gases  works  out  to  '21.9  per  cent,  of  the  whole  calorific 
value  of  the  fuel,  the  loss  by  formation  of  carbonic  j 
oxide  to  3.6  percent.,  and  that  due  to  the  evaporation  ; 
of  the  moisture  in  the  fuel  to  1.2  per  cent.  The 
sample  of  coal  analysed  being  free  from  clinker,  the 
4  per  cent,  of  clinker  may  roughly  be  said  to  correspond 
to  a  loss  of  about  3  per  cent,  of  the  whole  heat.  These 
quantities  add  up  to  91.7  per  cent,  of  the  whole  heat 
of  combustion  ;  and  the  balance  must  include,  among 
other  tilings,  all  losses  by  radiation.  The  amount 
of  water  evaporated  per  square  foot  of  tube  surface 
was  5.18  Ibs.  per  hour,  and  per  square  foot  of  total 
heating  surface  4.49  Ibs.  per  hour.  These  quantities 


have  to  be  multiplied  by  1.1  to  bring  them  to  stand- 
ard conditions.  The  average  rate  of  transmission  of 
heat  through  the  material  of  the  boiler  was  5244 
thermal  units  per  square  foot  of  heating  surface  per 
hour. 

Engine  Efficiencies. — The  measurement  of  feed 
water  shows  that  the  quantity  used  per  indicated 
horse-power  per  hour  was  only  14.98  Ibs.,  or  within 
the  limits  of  accuracy  of  measurement  15.0  Ibs. 
The  actual  heat  received  by  the  feed  water  per 
minute  was  528,700  thermal  units,  or  265.6  thermal 
units  per  indicated  horse-power  per  minute,  which. 
as  given  in  the  last  paragraph,  is  62  per  cent,  of  the 
whole  heat  of  combustion.  For  purposes  of  compar- 
ison with  a  perfect  engine,  it  may  be  assumed  that 
the  higher  limit  of  temperature  is  that  of  the  boiler 
steam,  363  degrees  Fahrenheit,  while  the  lower  limit 
may  be  taken  as  120  degrees  Fahrenheit.  It  was 
unfortunately  impossible  to  measure  the  temperature 
of  the  condensed  steam  as  it  entered  the  hot-well  ; 
but  with  the  good  vacuum  given  above,  it  is  not  prob- 
able that  it  differed  much  from  120  degrees  Fah- 
renheit. (The  temperature  corresponding  to  the 
mean  back  pressure  in  the  low-pressure  cylinder  is 
146  Fahrenheit.)  If  the  engine  had  been  "perfect" 
and  had  worked  between  363  degrees  and  120  degrees 
Fahrenheit,  it  should  have  turned  into  work  0.295  of 
the  heat  received  by  it.  The  heat  actually  turned 
into  work  was  85,240  thermal  units  per  minute,  show- 
ing efficiency  of  54.6  per  cent,  as  compared  with  a 
"  perfect  "  engine  working  between  the  same  limits 
of  temperature  and  receiving  the  same  quantity  of 
heat  per  minute.  This  is  a  high  efficiency,  but 
corresponds  with  the  low  feed  water  consumption. 
The  absolute  engine  efficiency,  or  ratio  of  the  heat 
turned  into  work  to  the  total  heat  received  by  the 
feed  water,  was  16.1  per  cent. 

Total  Efficiency. —  The  combined  efficiency  of  the 
boilers  and  engines,  or  ratio  of  heat  turned  into  work, 
to  the  total  heat  of  combustion  of  the  fuel,  was 
almost  exactly  10  per  cent. 

Steam  by  Indicator  Diagrams. — Careful  measure- 
ments of  all  the  diagrams  taken  have  been  made  to 
ascertain  the  proportion  of  steam  accounted  for  by 
them,  and  the  following  are  the  results,  the  actual 


'   .lAIA'AYA'   A'.NV/AYA. 


303 


weight  of  feed  water  used  per  revolution  having  !•< 

6.93  ii.s. 

fc*|  |j 

opoiti"ii  >  "                                    i  by 

•S3 

f« 

fs|a 

IglMOM. 

H 

I  "^ 

11 

I'er  cont. 

Strain   present  in  liiirli-piv--iire  eyl 

illiliT  alter  c-Ilt-c.tr.  wllrll  tllr  l 

lire  was    1  in  Hi-.    per   -cpiare   inch 

aticnv  ihr  atin                       ... 

5.34 

77.1 

•2-1.  '.> 

Strain  present  in   intermediate  cylin- 

der wh.-n  tin1    pre.--iiiv  was    111!  lli-. 

per  square   inch   ahove  tllr  ;tlnn>- 

plicre     

5.56 

80.2 

19.8 

Steam  present  in  lu\v-pre.-.-nre   eylin- 

der   near   end   id'  expan-i'in   when 

the  pressure  was  t    Ihs    per  square 

ineli  hclnw  the  atmosphere    -    - 

5.  'I  'I 

7:.  .; 

24.7 

each  expanded  diagram  being  the  mean  of  the 'two 
col-responding  ai'tual  ones.  The  full  lines  in  Fig. 
.'IS."/.'.  NIL  S,  show  these  mean  indicator  diagrams 
themselves,  drawn  to  the  same  scale  of  pressure  and 
of  volume,  and  placed  so  that  the  .space  to  tlie  left  of 
each  diagram  represents  the  clearance  space  in  the 
oorreepondjng  cylinder.  The  dotted  lines  in  Fig. 
No.  <s,  show  the  same  diagrams  set  back  in  such 
a  way  that  at  any  pressure  the  horizontal  distance 
A  1!  measures  the  actual  volume  of  working  steam  in 
the  cylinder  at  that  pressure,  as  represented  by  the 
dilVerence  between  the  volume  of  steam  of  that  press- 
ure in  the  cylinder  during  expansion  and  during 
compression,  or  A  E — A  D,  independently  altogether 
of  clearance  steam.  Each  horizontal  distance  or  ab- 
scissa of  the  dotted  curves,  such  as  A  B.  is  therefore 
directly  comparable  with  the  corresponding  abscissa 


••  M,'ti-»r"  Irials. 
8.   Expansion  of  Indicator  Diagrams,  Set  27. 


Fig.  383A. 


It  will  thus  be  seen   that  even  in   these  very  eco- 
nomical engines,  and  with  a  liberal  allowance  for  the 
MI  used   in    jackets,   which   unfortunately  could 
not  be  separately-measured,  there  must  have  been  a 
very  considerable  loss  due  to  cylinder  condensation. 


A  C  of  the  saturation  curve  8  S,  and  the  ratio  of  the 
one  to  the  other    -    at  any  pressure  gives  the  "  dry- 

*\:  \' 

ness  fraction,"  or  ratio  of  steam  to  mixed  steam  and 
Water  for  the  working  steam  at  that  pressure. 


Iii  Fig.  383&,  No.  8,  are  shown  expansions  of  the  set       In  Fig.  383£,  No.  9,  the  same  diagrams  are  treated 
of  indicator  diagrams  given  in  Fig.  383j,  Nos.  5  to  7, 1  in  a  somewhat  different  manner  proposed  by  Profes- 


304 


MODERN  STEAM  ENGINES. 


"Meteor" 

9.  Expansion  of  Indicator  Diagrams,  Set  27. 


I'olumt .     CU&LG    /tet> 


IW  C*u&t,o  Fttt. 


Fir/.  3837. 


sor  Unwin.  The  menu  indicator  diagrams  themselves 
are  here  again  expanded  in  the  usual  fashion,  as 
shown  by  the  full  lines.  The  expansion  line  of  each 
is  continued  to  the  end  of  the  stroke  at  B,  and  the 
horizontal  line  Q  A  B  is  drawn.  Then  the  length 
A  C  is  set  off  from  the  compression  line  (produced  if 
necessary)  to  represent  the  volume  of  the  whole  feed 
water  per  stroke  (less  jacket  water,  if  any)  if  it  were 
entirely  steam  of  the  pressure  at  B,  and  a  saturation 
curve  is  drawn  upward  through  C.  Then  at  any 
pressure  Q  B  represents  the  volume  of  the  whole 
steam  in  the  cylinder,  B  C  the  volume  of  the  steam 
corresponding  with  the  water  in  the  cylinder,  apart 
from  accumulated  water,  if  any,  while  Q  A  shows 
the  volume  of  steam  in  the  clearance  space  when  the 
same  pressure  is  reached  in  the  return  stroke.  The 
distance  A  B,  therefore,  represents  the  volume  of 


woiking  steam  and  the  ratio 


A  B 
A  C 


the  "  drvness  frac- 


tion "  in  the  same  way  as  the  similarly  lettered  dis- 
tances in  Fig.  383£,  No.  8. 

Coal  Consumption. — The  total  coal  put  on  the  fires, 
4005  pounds  per  hour,  corresponds  to  2.01  pounds  of 
coal  per  indicated  horse-power  per  hour  of  the  quality 
already  stated.  This  corresponds  to  1.76  pounds  of 
carbon  value  per  indicated  horse-power  per  hour,  or 


say  427  thermal  units  per  indicated  horse-power  per 
minute.  As  each  indicated  horse-power  per  minute 
is  equivalent  to  only  42.75  thermal  units,  this  makes 
the  combined  efficiency  of  boilers  and  engines  10.0 
per  cent.,  as  given  above. 

Speed  of  Vessel. — The  following  notes  from  the  log- 
bootc  of  the  ship  may  be  of  interest: 


Left  Pier  Head 
Biisi  Hock    - 
St.  Alb's  Head 
Ferns 

Flatvborough  Head 
Hnilsreon 
('miner 
Huseborough 
Cockle 


The  mean  speed  between  Leith  and  Cromer,  which 
practically  covers  the  trial,  was  therefore  14.6  knots. 

Supplementary  Trial. — Some  hours  after  the  main 
trial  was  finished,  and  after  all  the  fires  had  been 
cleaned,  the  stokehole  was  closed  and  fans  set  to 
work,  and  the  engine  driven  for  a  few  hours  at  full 
power  with  forced  draught.  The  particulars  of  the 
work  done  under  these  circumstances  are  given  in 


Distance  in 
Tim?.                 Nautical  Milm. 

0  50  A.  M. 

0 

2.20 

20 

3.40 

39J 

5.10 

62 

0.50  p.  M. 

175 

4.57 

236 

6.25 

257 

7.00 

265J 

7.46 

275 

run  .i/.i/.v.v/-:  I<:\<;I.\K. 


305 


K    S 


306 


MODERN  STEAM  EXGL\ES. 


Meteor"    Sufplemtnlary    Trioi/      Totle  1,   Stl   F. 
Revs    80  0  pur  nun.  Total  l.H.P   295*. 

19    ffigk-pnxture   cylinder.         IH.f  39*. 


'Meteor    Supp^fttitrtlary  Jriai     'Enguttg  /u2t  gter  astern* 
Jle\s  76  pa-  ntin..        Total  /HP    2660. 

22     High  -prejsra-c   cyluuUr        1HP  585.' 
ifrnn    Presiunt ,      Tap    enJt    5170W,,     Boliam   45-90  Us 


Top  aid-    31  50  /*»..    Boltcm    31  00  Its 


10          10         30          40         60         CO          70          60          00         KM 
20   Intermediate,  cyluukr        l.HP  952. 


Mean    rrannt.  Kf\rnd  54  05(*«.  Bottom.  3]  70 /As 


i 

10          20          30         40          M         60          10         80          9O        lOO*   «, 

23      InUrmtttiale.  cylinder.        1 H  P.    867. 
LhM  Means'  Prejturef,    Tap  end,    31  40  l&r.f      BoUcvn.   31-60  l&jt,   ,,     3 


10          to          90          M          SO         60          7O         80         00         10O 
21    Low  -  prttturt    cylinder        IffP  I608  "" 


Fftiton*,   TcFmd,  21  70  Mj  ,  BoUam.  21  60  M 

I  I  *  I  L 


10          20         JO          W          50          00         70          80          30         ICO 


U, 


24     Low- pressure    cylinjtr         I.  H.P.    1208 
^Metin.    Presturej.    Tfp  end 


.  383n. 


T:rble  I.  As  to  duigriwns  C,  E  and  F,  which  were 
taken  from  live  steam  admitted  to  the  first  receiver, 
it  may  be  explained  that  the  engine  has  an  auxiliary 
starting  valve  2J  inches  in  diameter,  which  enables 
tliis  to  be  done.  This  valve  is  occasionally  used 
when  there  is  any  fear  of  the  boiler  blowing  off,  so  as 
to  avoid  waste  of  steam  and  fresh  water.  This  occurs 
generally  for  only  a  minute  or  two  at  a  time.  The 
engines  run  from  two  to  three,  and  sometimes  as 
much  as  four,  revolutions  per  minute  faster,  and  it 
will  he  seen  that  the  diagrams  shown  in  Pig.  383m, 
Nos.  13  to  15,  and  Fig.  383n,  Nos.  19  to  21,  are  dis- 
torted, and  the  pressure  on  the  intermediate  piston 
much  increased. 


Table  I. — Supplementary  Trial  at  Full  1'iirrr  irith  Forced 
Di-initjht. 


* 

*• 

5 

Mean  Pres-sup-  per 
Square    Inrli. 

Indicated    II  (use-Power. 

£ 

h  "  "?         •- 

=f 

r_ 

e 

3     1   e 

g 

£            £ 

5 

r-S  5 

8 

J~  s 

.s.  •-. 

1  S 

3  t 

.i  % 

5   •' 
J    ^ 

B 

c  ^ 

-2 

_! 

~  ^ 

i  "^ 

£•3 

t  "r 

-i  "^ 

"^ 

3 

~  .— 

o 

•S 
fi 

P 

1 

i 
H 

f 

1Q 

|l 

45 

B 

P 

1" 

S 

Set. 

Lbs. 

lib. 

Lb« 

1,1  IS. 

1    II.  P. 

1.  II.  P. 

I.  H.  P. 

I.  H.  P. 

A 

146 

81.0 

60.9 

28.4 

IS.  5 

778 

832 

1  393 

3003 

B 

151 

81.0 

(i3  2  •'>  > 

19.0 

SOS 

sit 

1426 

3078 

C 

150 

S3.  1 

30.2  33!  7 

24.1 

397 

1013 

1863 

3273 

1) 

145 

7S.7 

f,4.  1 

25.5 

1C).  7 

796 

7i'7 

1  222 

2745 

E 

136 

80.0 

32.  9 

33.0 

21.8 

415 

957 

1617 

29S9 

F 

130 

80.0  31.2 

32.9 

21.6 

394 

952 

1608 

2954 

THE  MARL\E 


307 


rig.  383p. 


308 


MODERN  STEAM  ENGINES. 


Diagrams  A  and  B  are  believed  to  represent  the 
average  full  power  working  of  the  engines  going  north 
from  London  to  Leith,  when  the  steamer  always  runs 
with  forced  draught.  Diagrams  C,  Fig.  383m,  Nos. 
13  to  15,  correspond  to  the  conditions  of  A  and  B,  but 
with  live  steam  admitted  to  the  first  receiver. 

Diagrams  D,  Fig.  383m,  Nos.  16  to  18,  are  believed 
to  represent  the  average  working  of  the  engines  later 
on  in  the  same  full  power  run  when  the  tubes  are 
getting  dirty,  the  high-pressure  motion  being  drawn 
up  about  1  inch.  Diagrams  E  and  F,  Fig.  383n, 
Nos.  19  to  21,  correspond  to  the  conditions  of  D,  but 
with  live  steam  admitted  to  the  first  receiver.  When 
the  vessel  got  into  port  and  was  being  berthed,  it  was 
endeavored  to  get  a  set  of  indicator  diagrams  while 
the  engines  were  going  astern.  One  complete  set 
only  were  secured,  Fig.  3S3?i,  Nos.  22  to  24,  of  which 
the  following  are  the  particulars,  all  the  links  being 
in  full  gear : 

Boiler  pressure,  pounds  per  square  inch  above  atmos- 
phere, -      147 


Revolutions  per  minute, 

Vacuum  in  inches  of  mercury, 

Mean  pressure,  high-pressure  cylinder,  Ibs., 

intermediate 

low-pressure 


Indicated  horse-power  high-  pressure  cylinder, 
intermediate 
low-pressure 

Total, 


76 

-  27 
48.8 

-  31.5 
17.1 

I.  H.  P. 

-  585 
867 

-  1,208 

2,660 


It  is  interesting  to  compare  the  results  thus  ob- 
tained with  those  when  running  in  forward  gear 
(Fig.  383;',  Nos.  5  to  7)  as  showing  the  effect  of  alter- 
ing the  sequence  of  the  cranks,  which  under  these 
circumstances  follow  in  the  order — high,  low,  inter- 
mediate. 

Observers. — As  this  trial  was  perhaps  the  first 
marine  engine  trial  carried  out  on  any  large  scale  at 
sea  in  which  the  feed  water  was  measured  and  the 
coal  weighed  throughout  for  such  a  length  of  time, 


Tin-:  MAI;I.\E  EXGIXE. 


:VERSITY, 


309 


it  may  be  interesting  to  mention  tin-  stud'  which  was 
found  necessary  for  the  experiments.  The  work 
was  carried  on  by  two  relays  of  observers,  five  in 
each  relay,  keeping  alternate  four  hour  watches.  Mr. 
Frederick  Edwards  took  charge  of  one  watch,  consist- 
ing of  Mr.  By  ran  Donkin,  Jr.,  Mr.  A.  tl.  Ash- 
croft,  Professor  Beare,  Mr.  Beck  and  himself.  Pro- 
fessor Kennedy  took  charge  of  the  other  watch,  on 
which  were  also  Mr.  C.  L.  Simpson.  Mr.  It.  II.  \Villis, 
Mr.  B.  Bramwell.  and  Mr.  N.  1'iurnrtt.  One  man  in 


staff  encroached  upon,  an  extra  stoker  was  carried  in 
each  stokehold  for  the  purpose  of  filling  the  coal 
baskets  to  be  weighed.  An  extra  man  was  also 
carried  to  look  after  the  donkey  boiler,  which  for 
reasons  already  mentioned  had  to  be  kept  going 
during  the  whole  trip. 

Quadruple  Expansion  Engine. 


An    example  of  quadruple  expansion  is  given  in 


each  watch  took  the  feed  water  measurements  con- 
tinuously ;  with  him  was  an  engineer,  specially 
engaged  for  the  purpose,  to  stop  and  start  the  feed 
pump,  as  the  tanks  were  changed  in  the  manner  above 
described.  Two  observers  in  each  watch  took  the 
indicator  diagrams  and  other  observations  in  the 
engine-room,  and  two  others  attended  to  the  coal 
measurements,  one  in  each  stokehole ;  these  four  inter- 
changed places  after  two  hours'  work.  As  it  was 
necessary  that  the  ordinary  work  of  the  ship  should 
not  be  interfered  with,  or  the  time  of  the  engineer's 


383r. 


Figs.  3S3p,  383g,  383r,  and  383s,  which  are  taken  from 
Engineering. 

Fig.  383p  is  a  perspective  view,  Fig.  383g  an  end 
elevation,  Fig.  383r  a  front  elevation,  and  Fig.  383s  a 
plan.  It  will  be  seen  that  the  arrangement  is  peculiar, 
all  the  cylinders  being  placed  on  one  level.  The 
advantage  in  getting  a  lower  engine  will  be  at  once 
apparent,  and  this  at  least  should  be  a  very  desirable 
feature  in  applying  these  engines  to  warships.  As 
neither  of  the  two  piston-rods  of  each  pair  of  cylin- 
ders can  be  over  the  crankshaft,  the  axis  of  which  is 


310 


MODERN  STEAM  ENGINES. 


in  the  usual  place  in  the  middle  of  the  engine  bed, 
the  ordinary  connecting  rod  is  replaced  by  a  steel 
casting,  as  shown  in  Fig.  383gr.  Attached  to  the 
crosshead  of  each  piston-rod  is  a  link,  the  lower  end 
of  these  links  being  attached  to  the  triangular  steel 
casting  which  takes  the  place  of  the  connecting-rod. 
The  lower  end  of  the  casting  has  brasses  in  which  the 
crank-pin  works  in  the  usual  way.  There  is  a  lever, 
or  rock  arm,  which  pivots  on  a  pin  in  the  engine 
framing,  the  other  end  being  attached  to  a  pin  on 


and  not  into  the  steam  chest.  From  thence  it  is 
admitted  to  the  cylinder  through  the  centre  cylinder 
port,  and,  having  done  its  work,  exhausts  into  the 
casing.  It  must  now  be  explained  that  the  valves  to 
each  pair  of  cylinders  are  placed  one  above  the  other 
on  one  valve-rod,  and  work  in  one  steam  chest  common 
to  both.  It  will  be  seen,  therefore,  why  it  is  necessary 
for  the  boiler  steam  to  be  admitted  inside  the  valve, 
or,  in  other  words,  between  the  flanges,  as  otherwise 
the  high  pressure  steam  would  pass  into  the  second 


the  connecting  piece  as  shown  in  Fig.  383g.  In  the 
engine  in  question  a  prolongation  of  this  arm  is  used 
to  work  the  air  pump,  etc.  The  two  pistons  of  each 
pair  of  cylinders  ascend  and  descend  not  quite 
together,  one  being  a  little  in  advance  of  the  other. 
Consequently  there  is  no  dead  centre  for  either  crank. 
The  sequence  of  the  cylinders  will  be  seen  from  the 
plan,  Fig.  383s.  Steam  is  admitted  to  the  high- 
pressure  cylinder  by  means  of  the  piston  valve  placed 
between  the  first  two  cylinders.  The  steam  passes 
first  into  the  space  between  the  flanges  of  the  valve, 


383s. 


cylinder  as  well  as  the  first,  the  valve  chest  space 
being  common  to  both  valves  and  cylinders.  The 
steam  escaping  from  the  first  cylinder  fills  the  valve 
chest,  and  is  admitted  to  the  second  cylinder  in  the 
usual  way,  the  exhaust  this  time  being  carried  by 
the  inside  of  the  valve.  Steam  is  then  taken  to  the 
two  next  cylinders,  and  the  same  action  is  gone 
through  once  more,  until  the  steam  escapes  to  the 
condenser  in  the  usual  way. 

The  valves  are  worked  by  eccentrics  and  reversed 
by  link  motion,  but  the  arrangement  is  necessarily 


THE  MARINE  ENGINE. 


311 


peculiar.  The  valves  for  the  third  and  fourth  cylinders 
are  placed  directly  over  the  crankshaft,  and  can  be 
worked  from  eccentrics  in  the  usual  way.  The  valves 
for  the  first  and  second  cylinders,  however,  are  con- 
siderably on  one  side  of  the  fore-and-aft  centre  line. 
In  order  to  work  the  valve-rod  common  to  these,  an 
arm  or  connecting  rod  is  taken  from  each  of  the  eccen- 
tric straps,  and  these  arms  work  the  link  motion  by 
means  of  a  bell-crank  lever  attached  to  the  engine 
bed.  In  Fig.  3S3<y  the  arm  of  one  eccentric  can  be 
plainly  seen  together  with  the  bell-crank  lever,  and 
the  connecting-rod  carrying  the  motion  to  the  solid 
bar  link.  The  reversing  links  are  placed  one  imme- 
diately in  front  of  the  other,  and  are  pulled  over  by 
one  lever  and  drag  links.  It  will  therefore  be  seen 
that  only  two  eccentrics  are  used  for  all  four  cylinders, 
and  only  one  would  be  required  in  a  non-reversing 
engine. 
The  standards  of  the  engine  are  used  as  crosshead 


guides,  and  the  rubbing  surface  is  less  than  usual, 
but  with  the  arrangement  of  connection  between 
crosshead  and  crank-pin  here  shown  the  side  thrust 
is  very  small,  and  there  is  little  wear  on  the  slipper 
guides. 

The  advantages  the  makers  claim  for  this  design 
of  engines  are,  that  free  access  is  offered  to  each  cyl- 

!  inder,  less  fore-and-aft  space  is  taken  up,  and  also 
less  height.  There  are  fewer  wearing  parts  and  less 

i  attention  in  running  is  required,  consequently  a 
cheaper  upkeep  is  obtained.  The  two  cranks  being 
placed  directly  opposite  each  other  give  a  balance  of 
moving  parts.  It  is  also  claimed  that  the  turning 
action  of  the  four  pistons  on  the  crankshaft  is  equal 
to  four  cranks  at  right  angles. 

These  engines  are,  we  are  informed,  designed  to 
work  at  a  pressure  of  180  pounds  to  the  square  inch, 
and  have  been  run  light  at  400  revolutions  per 
minute. 


•ME 


CHAPTER  XII. 


VARIOUS  APPLICATIONS  OF  THE  STEAM  ENGINE. 


THE  TRACTION  ENGINE. 

A  traction  engine  consists  of  an  ordinary  engine  and 
boiler,  mounted  upon  two  pair  of  wheels,  the  front  pair 
of  which  are  used  for  steering  purposes,  and  the  rear 
pair  for  propelling  the  engine  and  hauling  loads.  The 
engine  is  provided  with  a  reversing  gear  and  a  pump 
for  feeding  the  boiler,  and  in  some  cases  with  a  belt 
wheel  for  driving  Agricultural  Machinery.  To  obtain 
sufficient  power  without  the  employment  of  a  large  pis- 
ton and  a  slow  piston  speed,  the  crank-shaft  delivers 
the  power  to  the  traction  wheels,  through  a  train  of 
gear  wheels,  which  reduce  the  revolutions  of  the  latter 
in  the  proportion  of  20  to  30  revolutions  of  the  crank- 
shaft, to  one  revolution  of  the  traction  wheels,  the  pro- 
portion of  the  gearing  depending  upon  the  class  of 
work  the  engine  is  intended  for,  and  agreeing  with  a 
speed  of  2  or  3  miles  per  hour.  The  driving  pinion 
of  this  gearing  is  thrown  out  of  gear  when  the  engine 
is  to  be  used  for  driving  threshing,  or  other  farm 
machines.  The  boiler  of  a  traction  engine  should  be 
free  to  expand  and  contract,  without  being  resisted  by 
the  engine  frame,  which  would  otherwise  strain  the 
boiler  and  hasten  its  destruction.  The  boiler  should 
have  a  spring  or  cushioned  seating  upon  both  axles. 
312 


The  Frick  Traction  Engine. 

The  manner  in  which  these  requirements  are  fulfilled 
in  the  Frick  Company's  Traction  Engine,  is  shown  in 
the  following  illustrations,  in  which  fig.  384  is  a  perspec- 
tive view  of  the  engine,  fig.  385  a  plan  of  the  engine 
removed  from  the  boiler,  and  shown  partly  in  section, 
and  fig.  386  a  side  elevation  of  the  engine  removed 
from  the  boiler,  and  shown  partly  in  section. 

The  frame  of  the  engine  is  one  continuous  casting, 
having  at  its  cylinder  end,  an  eye  e,  through  which 
passes  a  pin  P  secured  in  a  bracket  bolted  to  the  top  of 
the  boiler,  so  that  as  the  boiler  lengthens  or  shortens, 
from  expansion  or  contraction,  the  pin  may  pass  through 
the  eye  e,  leaving  the  boiler  and  the  engine  connection 
free  from  expansion  strains;  at  the  other  end  the  engine 
frame  is  bolted  to  two  side  plates  S  and  S',  fig.  385a  which 
clear  the  boiler,  and  connect  to  two  channel  irons 
which  pass  to  the  front  end  of  the  fire-box,  curve 
inwards,  and  thence  connect  to  the  saddle  block 
of  the  front  axle.  This  saddle  block  is  provided  with 
an  expansion  joint,  permitting  the  boiler  to  expand  and 
contract  without  being  resisted  by  this  part  of  the  fram- 
ing, and  also  with  a  spring,  or  elastic  seat,  upon  which 
the  boiler  may  ride  easily. 


Tin:  •/•//.  i  <  n<>.\  I-:M;I\!-:. 


313 


/ty.  384. 

The  Prick  Traction  Engine. 


314 


MODERN  STEAM  ENGINES. 


7 HE  ri;.\crn>\  !-:.\<;I\E. 


31 5 


The  steering  is  done  l>y  swinging  flu-  front  axle.  by 
means  of  the  chains  operated  liy  the  worm  and  worm 
wheel  shown  in  th(>  jKTsiK>cti\v  view  fig.  :;.S4.  To  pro- 
vide an  elastic  connection  to  this  part  of  tlic  mechanism, 
.•mil  thus  avoid  breakage,  the  chain  is  provided  with  a 
spiral  spring,  which  is  clearly  seen  in  the  perspective 
view. 

The  engine   has  a   plain   slide  valve   and    a   reversing 

motion,  in  which  tl -centric  is  shifted  across  the  shaft, 

both  for  varying  the  point  of  cut-off  and   for   reversing 
purposes. 

The    feed   pump  is   opt-ratecl    from    the  engine  cross- 


h\,j.  885". 

head,  and  forces  the  feed  water  through  a  heater  placed 
lengthwise  of  the  engine  frame 

K'-:erring  now  to  tigs.  :i,So  and  3.H6.  the  cylinder  and 
I 'and  wheel  are  shown  in  section,  and  the  pump  and 
heater  partly  in  section. 

The  connecting-rod  has  a  key  at  the  cross-head  end. 
and  an  adjusting  screw  at  the  crank-end,  so  that  the 
length  of  tiie  rod  is  kept  as  constant  as  possible,  because 
while  the  passage  of  the  key  through  the  strap  acts  to 
lengthen  it,  screwing  up  the  set  screw  acts  to  shorten  it. 
The  end  of  this  set  screw  s'  abuts  against  a  plate  upon 
which  the  back  brass  beds,  the  plate  preventing  the  set 
screw  end  from  indenting  the  brass. 

The  crank  is  balanced  by  the  balance  weight,  or  bob 
c.  The  wear  of  the  main  bearing  is  taken  up  by  set 
screws  s  s. 

The  driving  pinion  has  a  clutch  connection  witli  the 
band  wheel,  so  that  when  used  for  driving  agricultural 
machines,  it  can  be  moved  endwise  upon  the  crank-shaft, 
and  out  of  gear  with  the  train  of  gearing  used  for  trac- 
tion purposes.  When  the  pinion  is  in  gear  with  the 


traction  gears,  it  is  still  in  gear  with  the  band   wheel 
which  serves  as  a  fly-wheel  for  the  engine. 


THK   KKVKItSIM)   (iKAK. 

The  engine  is  reversed,  or  the  point  of  cut-off  varied 
by  means  of  shifting  the  eccentric  across  the  crank- 
shaft, the  construction  being  as  follows: 

In  fig.  3X7  D  is  a  disk  (shown  also  at  D  in  fig.  385) 
which  is  fast  upon  the  crank-shaft,  and  to  which  the 
eccentric  E  is  pivoted  at  b,  so  tliat  from  J  as  a  center, 
the  eccentric  can  be  swung  across  the  crank-shaft.  At 
//'  is  a  stop  pin,  which  is  threaded  into  the  eccentric 
flange,  and  moves  in  the  slot  a,  which  is  an  arc  of  a 
circle  of  which  b  is  the  center.  The  limit  of  eccentric 
motion  across  the  shaft,  is  determined  by  this  pin  b'  seat- 
ing against  the  end  of  slot  a,  and  it  follows,  that  when 
the  eccentric  is  moved  into  position  for  full  gear,  for 
either  the  backward  or  forward  motion,  it  is  driven  by 
the  two  pins  b  and  b'.  The  limits  of  eccentric  motion 
across  tiie  shaft,  is  denoted  by  the  dotted  lines  x  x',  the 
mid-position  being  denoted  by  the  dotted  line  y. 

The  method  of  shifting  the  eccentric  across  the  shaft, 
is  as  follows:  Fixed  to  the  eccentric  is  a  cross  rack  F 
meshing  with  a  sliding  rack  J,  which  may  be  moved 
endways  and  parallel  with  the  crank-shaft.  The  teet'.i 
of  these  two  racks  are  at  an  angle  of  45°  across  ths 
width  of  the  rack,  so  that  by  moving  the  sliding  rack 
etui  wise,  the  cross  rack  F  shifts  the  eccentric  E. 

Tli  cross-rack  F  is  operated  by  a  piece  r  v,  that  is 
fixed  to  the  sleeve  T,  which  may  be  moved  endways 
upon  the  shaft,  by  means  of  a  yoke  P,  whose  two  trun- 
nions t  /'  connect  to  the  forked  or  double-eye  end  of 
the  reversing  lever.  At  n  is  a  link  to  which  the  rever 
sing  lever  is  pivoted,  this  link  being  pivoted  at  m  so  as 
to  permit  of  the  lever  accomodating  itself  to  the  motion 
of  the  sleeve  T,  along  the  shaft. 

The  pump  rod  or  plunger,  is  driven  from  the' cross- 
head,  the  pump  barrel  being  bolted  to  the  engine  frame. 
The  suction  valve  v  is  provided  with  a  wheel  W,  fig. 
386,  whose  spindle  end  adjusts  the  height  to  which  the 
suction  valve  can  lift,  and  thus  governs  the  rate  of 
boiler  feed. 

From  the  delivery  valve  v'  the    feed    water    passes 


316 


MODERN  STEAM  ENGINES. 


I 
fi 


of 

00 


THE   TRACTION  ENGINE. 


317 


5 


MODERX  STEAM  EA'GLVES. 


througli  pipes  p'  and  p,  in  the  heater  H,  and  out  at  u, 

whence  it  passes  into  the  boiler.     The  exhaust  steam 

"  passes  through  the  heater  to  an  exhaust  nozzle  in  the 

smoke  box,  and  thus  assists  the  draught  of  the  boiler. 

The  connection  between  the  driving  gears  and  the 
traction  wheels,  is  as  follows:  To  the  arms  of  the 
traction  wheel  is  secured  an  annular  ring  provided  with 
lugs,  to  which  are  attached  spiral  springs,  the  other 
ends  of  which  are  attached  to  similar  lugs  upon  the 
iinns  of  tlio  driving  gear.  IIPMOP  these  springs  act  as  an 


passing  into  the  cylinder  is  made  as  follows:  The  crown 
sheet  of  the  fire-box  is  inclined  to  the  rear,  as  seen  in  fig. 
388,  and  a  dry  steam  chamber  is  provided,  as  shown, 
The  dry  pipe  takes  steam  at  the  top  of  the  fire-box, 
and  discharges  it  into  the  dry  steam  chamber. 

When  the  engine  is  descending,  as  in  the  figure,  the 
top  of  the  fire-box  remains  covered  with  water,  and  the 
steam  passes  from  the  fire-box  through  the  dry  pipe 
into  the  dry  steam  chamber,  while  when  the  engine  is 
ascending,  the  steam  fills  the  dome,  and  what  little 


388. 


elastic  connection,  which  permits  the  traction  wheel  to 
move  within  certain  limits,  either  vertically  or  horizon- 
tally, provision  being  made  in  the  construction  of  the 
wheel  and  axle  connection,  to  permit  of  such  traction 
wheel  motion,  without  changing  the  position  of  the 
driving  gear  with  relation  to  the  pinion  that  drives  it. 
This  not  only  enables  the  boiler  to  ride  easily  when  the 
engine  is  passing  over  rough  roads,  but  it  avoids  the 
breakage  of  gear  teeth,  that  is  apt  to  occur  where  the 
connections  are  too  rigid. 

When  the  engine  is  to  be  used  in  very  hilly  districts 
provision  for  preventing  the  water  in  the  boiler   from 


water  that  may  pass  through  the  dry  pipe  will  be  evap- 
orated in  the  dry  steam  chamber. 

The  pipe  at  B  is  a  blast  pipe  for  forcing  the  draught 
by  a  steam  jet. 


THE  PORTABLE  ENGINE. 


A  Portable  Engine  is  one  that  is  mounted  upon 
wheels,  and  a  semi  portable  engine  one  that  can  Lo 
moved  from  place  to  place  without  requiring  to  be  erect- 
ed upon  a  foundation.  In  portable  engines  for  agricul- 


[VERSITY 


tural  purposes,  this  is  usually  accomplished  by  mount, 
ing  the  engine  ui»'ii  the  boiler,  and  the  boiler  upon 

-.  For  the  work  room-  -mail  biisines.-es 

carried  on  in  cities,  portable  m^ines  are  sometimes 
attached  to  th«-  vertical  boilers,  <  Generally 

liowever.  the  vertical  boiler  is  mounted  upon  an  iron 

i'late  or  frame,  to  which  the  engine  is  bolted 
independently  of  the  boiler,  this  being  the  plan  also 
adopted  for  hoisting  engines. 


319 


box  to  the  shell  of  the  boiler  are  threaded  at  the  ends 
and  rivet  ted  over. 

t  are  angle  irons,  for  staying  the  tube  sheet, 
aii'i  ;ii  /'.  an  angle  iron  for  staying  the  plate  at  that 
end  of  the  hoiler.  An  end  view  of  theeugiue.showing 
its  attachment  to  the.  boiler,  is  shown  in  Fig.  391,  the 
a,xle  is  curved  at  A,  the  brackets  B  being  bolted  to  the 
boiler,  which  reals  on  a  band,  having  at  C  nuts,  which 
secure  the  band  to  the  brackets  B  B. 


Fig.  389  is  a  side  elevation  of  the  Frick  Company,s 
Portable  Engine  on  wheels,  and  fig.  390  is  a  sectional 
view  of  the  boiler.  The  construction  of  the  engine 
corresponds  with  that  already  shown  with  reference  to 
the  traction  engine.  The  boiler  is  of  the  locomotive 
pattern,  the  water  surrounding  the  fire-box,  except  at 
the  furnace  and  ash-pit  doors.  The  stays  from  the  fire- 


389. 


Fig.  392  represents  a  semi-portable  engine,  by  the 
Lidgerwood  Manufacturing  Company. 

The  boiler  is  mounted  upon  an  iron  base,  forming  a 
foundation  for  the  engine,  and  in  which  the  crank-shaft 
bearings  are  situated.  A  single  guide-bar  placed  above 
the  cross-head  is  used,  and  a  Pickering  governor. 

Portable  engines  usually  have  plain  D  slide  valves. 


320 


MODERN  STEAM  ENGINES. 


O 
C5 


THE  PORTABLE  EXGJXE. 


321 


Fiy.   391. 
End  View  of  the  Frick  Portable  Engine. 


Colwell's  Engine  For  Sugar  Mitts. 


Fig.  393  is  a  representative  of  the  class  of  beam 
engine  used  upon  sugar  estates  for  driving  the  cane- 
crushing  rolls,  the  driving  pinion  being  shown  on  the 


crank-shaft.  The  link  motion  is  moved  for  different 
points  of  cut-off  by  a  segmental  rack,  and  worm,  as 
shown,  and  is  counter-balanced  by  a  weight  suspended 
to  one  end  of  the  rack.  A  common  D  valve  is  employ- 
ed, and  a  throttling  governor.  Motion  from  the  link- 
block  rod  to  the  valve-rod  is  conveyed  through  a  rock- 
shaft. 


322 


MODERN  STEAM  ENGINES. 


„%  i        j 


J:.\<n.\K 


324 


MODERN  STEAM  ENGINES. 


'/•///.    >/7.. I.)/  FIRE  E.\CIM-:. 


325 


THE  STKAM   FIHK   EXCIXE. 

Steam  fin'  engines  may  be  divided  into  two  principal 
classr<.  those  with  roiarv.  niiil  those  \vilh  reciprocating 
pumps.  \\~hcn  reciprocal  ing  pumps  arc  used,  the  steam 
and  pomp  pistODS  Are  usually  on  one  roil,  ami  belween 
tlic  two  is  a  yoke,  such  as  was  snown  in  Fig.  71.  this 
yoki'  being  employed  to  drive  the  lly-w: 

The  steam  cylinders  usualiy  have  plain  D  slide  valves 
the  Steam  following  for    ihree-uuarters   or    more,  of   the 
stroke.      Tha'pump  valves  are  usually   Hat    rubber   - 
with  spiral  springs    behind   them. 

Tin;  air  chain!"  be    pumps   are  so   constructed, 

as  to  let  the  water  they  contain  be  <listurl>ecl  as  little 
as  ]>ossible  by  the  delivery  water  I' mm  the,  pump,  be 
cause  the  water  gradually  absorbs  the  air  from  the 
i-hamlier.  and  the  presence  of  the  air  funds  to  break  up 
the  water  column  after  it  has  left  the  hose  noy.zle.  In 
some  cases,  the  air  chambers  are.  for  the  above  purpose, 
provided  wiih  long  necks  in  which  the  water  may  he, 
as  nearly  as  may  be,  undisturbed.  Jn  others,  a  pipe 
extends  up  within  the  chamber,  thus  separating  the 
water  and  air. 

A  delivery  pressure  greater  than  the  steam  pressure 
is  obtained  by  making  the  steam  piston  of  larger  dia- 
meter than  the  pump  piston. 

When  a  rotary  pump  is  used,  a  delivery  pressure 
greater  than  the  steam  pressure  may  be  obtained  in  two 
ways,  first  by  reducing  the  diameter  of  the  pump,  and 
•udly,  by  making  the  pump  cylinder  shorter  than 
the  steam  cylinder.  A  rotary  pump  possesses  the  ad- 
vantage that  it  requires  no  valves,  and  the  suction  and 
delivery  water  is  kept  in  continuous  motion,  unchecked 
by  the  rise  and  fall  of  valves.  Rotary  steam  cylinders 
are  less  economical  of  fuel  than  reciprocating  ones,  but 
in  a  steam  fire  engine,  efficiency  is  of  the  greater  im- 
portance than  fuel  economy. 

Hie  Silsby  Steam  Fire  Engine. 

Fig.  394  represents  a  steam  fire  engine  with  rotary 
steam  cylinder  and  pnmp,  and  Fig.  .395  a  longitudinal 
section  through  the  engine  and  boiler,  the  construction 


being  as  follows:  What  may  be  termed  the  fire  box, 
nds  downwards  from  the  plate  a,  which  supports  a 
series  of  double  tubes  that  extend  down  towards  the 
lire.  These  doubie  tube)  are  one  within  the  other,  the 
inner  tube  having  a  V  snaped  opening  at  the  bottom,  so 
that  the  water  can  pass  down  through  the  inner  tube 
and  up  through  the  space  between  the  inner  and  outer 
tube,  the  latter  being  closed  at  its  lower  end,  and  being 
surrounded  by  the  heat  in  the  firebox. 

The  lire  box  has  water  legs,  or  in  other  words,  there 
is  water,  between  its  sides  and  the  shell  of  the  boiler. 
'Ih rough  the  body  of  the  boiler  from  a  to  b  are  the 
smoke  Hues,  through  which  the  heat  and  products  of 
combustion  pass  to  the  chimney.  The  dry  pipe  through 
which  steam  is  taken  for  the  engine,  extends  around 
the  boiler  as  shown  at  C  C,  D  being  the  steam  pipe 
for  the  roury  engine  E.  The  exhaust  pipe  is  shown 
at  F,  extending  up  to  G,  where  there  is  an  exhaust 
nozzle  whose  area  of  opening  may  be  either  opened  or 
closed  to  regulate  the  draft  for  the  fire.  This  nozzle 
consists  of  a  cone  having  openings  on  two  sides,  and 
capable  of  adjustment  vertically,  in  a  coned  seat  at  the 
top  of  the  exhaust  pipe.  When  the  cone  is  raised  out 
of  its  seat,  the  exhaust  is  more  free,  whereas  when  it 
is  lowered,  the  area  of  exhaust  opening  is  reduced,  the 
stearn  escapes  with  a  greater  velocity  and,  as  it  carries 
with  it  up  the  chimney  the  contents  of  the  smoke  box, 
the  draft  is  forced.  The  constuction  of  the  engine  is 
seen  in  the  cross-sectional  view  at  H.  It  consists  of 
two  intermeshmg  cams  upon  shafts  that  are  geared 
together  by  the  gearing  at  J  K,  in  Fig.  395,  so  that 
the  two  cams  are  driven  independently,  which  relieves 
the  intermeshing  parts  of  strain  Eacli  cam  has  two 
strips,  which  have  contact  with  the  circumferential  bore 
of  the  cylinder,  to  maintain  a  steam  tight  fit,  and  these 
strips  follow  up  the  wear.  The  construction  of  the 
pump  is  similar,  except  that  each  cam  has  three  strips 
for  bearing  against  the  cylinder  bore. 

The  globe  valve  at  N  admits  a  portion  of  the  exhaust 
steam  into  L.  to  heat  the  feed  water,  the  pipe  from  the 
engine  extending  down  into  the  heater  L,  and  beimc 
perforated  to  distribute  the  steam  through  the  water. 
The  pipe  whose  exit  is  shown  at  M,  is  merely  an  over- 
flow. 

There  are  two  methods  of  feeding  the  boiler  as  fol- 


MODERN  STEAM  ENGINES. 


327 


lows:     g  g,  are  a  pair  of  gears,  a  crank-pin  on  the  lower 
one  operating    the    vn.l  h    of  tin-    pump  />.    wl 
water    from  the    heater  L  thvoii.irli    tin-    suction  pipe  N. 
where  there  is  a  glone  valve  to  regulate   tin:  ainoi:i 
feed.     Second,  a]'  'lived  from  tin-  niiiin   pump 

P,  to  S,  so  that  by   opening  a  valve,  the   water  can  pass 
through  pipe  e,  and  through  /  into   •  without 

passing  through  putnp  />.     This   method  of  t'ee'iinsj  can 
be  employed   when   the  pressure   in  the   air  chamber 


HOISTING   EN-RINKS. 

Fig.  .TOO  represents  Mundy's  hoisting  engine,  ii 
which  the  cylinder  is  bolted  to  the  side  of  a  frame, 
upon  which  the  boiler  is  mounted.  The  connecting 
rod  drives  a  disc,  on  whose  shaft  is  a  pinion  that  drive* 
t'r.e  hoisiing  drum  or  drums,  as  the  case  may  be,  througl! 
a  simple  or  compound  train  of  gearing,  according  ta 
the  weight  the  engine  ia  designed  to  lift. 


Fig.  396. 

Mundy's  Hoisting  Engine. 


exceeds  that  in  the  boiler,  and  to  obtain  the  required 
pressure,  the  discharge  gate  of  the  pump  may  be  par- 
tially closed.  To  prevent  the  feed  pump  p  from  freez- 
ing in  severe  weather,  a  pipe  is  provided,  which  may  be 
used  to  admit  steam  from  the  boiler  to  the  pump.  To 
promote  the  draft,  a  pipe  connects  from  r  to  the  ash-pit, 
thus  allowing  the  main  pump  P  (from  which  r  recieves 
water)  to  wet  the  ashes. 


Fig-  397  is  an  end  view  of  the  frame,  showing  the 
construction  of  the  friction  device  through  which  the 
power  is  transferred  from  the  crank  disc  on  the  right, 
to  the  gear  on  the  left,  and  it  is  seen,  that  in  this  ex- 
ample, the  crank-shaft  operates  a  spur  gear,  on  whose 
side  is  secured  a  cone,  formed  of  pieces  of  wood,  whose 
end  grain  is  radial  from  the  gear  axis. 
The  end  of  the  drum  is  provided  with  a  conical  seat, 


328 


MODERN  STEAM  EXGL\KS. 


into  which  the  wooden  cone  may  be  forced  by  the  lever 


Fig.  397. 
Mundy's  Friction  Drum. 


shown  at  the  right  hand  end  of  the  drum  shaft.  This 
lever  operates  a  screw,  which  moves  the  drum  endways 
on  its  shaft,  to  engage  or  disengage  the:  cones,  as  may 
bo  required  for  raising  or  lowering  the  load. 

Each  drum  is  provided  with  a  ratchet  and  pawl,  as 
shown,  for  holding  the  load  independently  of  the  fric- 
tion cones,  or  of  the  piston  power. 

A  steam  pump  for  boiler  feeding  is  shown  attached 
to  the  boiler.  Hoisting  engines  are  provided  with  flat 
D  slide-valves,  and  with  link  motions  for  reversing  pur- 
poses. 

Fig.    398  shows  a  single   cylinder   and   single    drum 


Fi?j.  398. 
The  Lidgerwood  Hoisting  Engine. 


M:MI-I;<>T.\I;Y  AND  ROTARY  I-:.\<;IM-:.\ 


hoisting  ong'.:  nicted  dy  the  Lidgerwood  Maim 

factoring  <  'oiimany.  and  havinic  ..-lion   ap; 

to  the  drum.      A    similar  OS  -d,  with  u 


Fig.  399. 

cylinder  on  each  side  of  the  frame,  the  cranks  being  at 
right,  angles. 

The  lowering  of    the  load  is  effected   by  partially  re- 
leasing the  grip  of  the  friction  cones  of  the  hoisting 

drum. 


Robertson's  Semi-Rotary  Engine. 


Fig.  •".!»'.'  shows  a  stationary  hoisting  engine,  with 
two  cylinders  and  link  motion  reversing  gear. 

In  semi-rotary  engines  the  pistons  reciprocate  in  an 
arc  of  a  circle,  and  the  great  difficulty  in  this  form  of 
engine  has  Wn,  that  the  piston  power  acts  to  bend 
the  piston,  and  cause  it  to  bind  in  the  cylinder  bore. 

In  Robertson's  engine,  however,  this  defect  is  elimin- 
ated, the  construction  being  as  follows:  Referring  to 
Figs.  400  and  401,  aa  is  the  cylinder,  B  B  the  piston, 
c  a  center  piece  to  which  B  B  is  bolted,  and  which  has 
journal-bearing  in  boxes  provided  upon  the  cylinder 
or  frame,  to  which  one  end  of  the  connecting-rod  F  is 
pivoted  by  means  of  can  ordinary  crank-pin.  G  is  the 
crank,  and  M  the  fly-wheel.  H  is  an  ordinary  eccentric 


to  operate  the  slide  valvo,  which  is  of  the  three-port 
lype.  N  is  it  piece  separating  the  two  chambers  a,  a.  the 
exhaust  pint  pacing  through  il,  and  the  steam  ports 
being  cine  on  each  side  of  it.  E  is  a  gland  for  packing 
the  piston  Referring  now  to  Fig.  401,  it  will  be  ob- 
<1  that  in  one  resting  we  have  the  cylinder,  the 
frame  and  the'  fly-wheel  bearings.  The  bearings  upon 
which  the  piston  vibratos,  are  also  cast  solid  upon  the 
same  casting.  The  pistons  B  are  firmly  bolted  to  the 
miiln  arrying  the  crank-pin,  the  object  being  to 

facilitate'  turning  the  pistons  in  the  lathe. 

To  secure,  I.eyond  peradventure,  the  pistons  upon  the 
miiidie  piece,  they  arc-  let  or  recessed  into  it. 

'I  he  pistons,  it  will  be  observed,  do  not  fit  against 
ihe  sides  of  the  cylinder,  except  over  a  small  projecting 
piece-  at  th»!  top,  which  serves  as  an  abutment  for  the 
packing,  the  space  for  which  is  shown  between  it  and 
the  end  of  the  gland  E. 

The  space  between  the  pistons  and  the  cylinder  bore 
is  made  to  be  as  small  as  possible,  and  represents  the 
clearance  found  in  the  pa-sages  incidental  to  three-port- 
ed valves.  The  pistons  B  B  are  solid  castings,  whose 
strength  insures  them  against  spring.  The  packing, 
which  keeps  them  steam-tight,  represents  the  steam 
packing  of  an  ordinary  piston,  the  gland  and  its  pack- 
ing being  dispensed  with.  A  feature  of  this  plan  is, 
that  any  piston  leak  becomes  apparent  at  once,  and  the 
nuts  being  on  the  outside,  the  packing  may  be  tight- 
ened and  the  leak  stopped  immediately,  without  stop- 
ping the  engine.  Steam  is  admitted  alternately  through 
the  ports  on  the  right  and  left  hand  of  the  pistons. 
The  eccentric  rod  is  hooked  to  the  rocker  arm  I,  the 
latter  being  provided  with  a  handle,  whereby  to  oper- 
ate the  valve  by  hand  when  starting  the  engine.  K  is 
the  valve  stem,  and  L  the  steam  chest. 

The  Rotary  Engine. 

A  rotary  engine  is  one  in  which  the  piston  revolves 
with  the  shaft,  hence  the  length  of  the  stroke  is  the 
path  of  the  piston,  around  the  cylinder  bore.  In  some 
forms  ot  rotary  engines,  cam  shaped  pistons,  such  as 
was  shown  in  Fig.  395,  are  employed.  In  others,  the 
piston  head  carries  small  sliding  pieces,  which  are 


330 


MODERN  STEAM  ESG1XES. 


Fi<j.  401. 
Bobertson's  Semi-Rotary  Engine. 


THE  ROTARY  A.\V,7.V/.. 


331 


ino'-ed  in  and  out,  to  pass  an  abutment  l>y  cam  mo: 
while   in  others,  the    abutment    itself  is  moved.  In    allow 
the  piston  to  paaa 

A  rotary  engine    )  that  there 

is  no  reversal  of  motion  of  tho  piston,  etc.,  at  the  en. Is 
of  tho  stroke,  and  of  comparative  incxpcnsivencss  to 
make. 


I  ML',  which  is  a  longitudinal  section  on  a  vertical  plane 
ii.-iralell  with  the  shaft,  ami  Fig.  40.3  an  end  elevation, 
with  the  cylinder  cover  removed,  The  cylinder  is  divi- 
ded by  a  central  partition  A.  On  the  shaft  I?  are  two 
pistons  C,  which  pass  through  abutment  rings  E. 

These  rings  fit,  at  their  ends,  into  recesses  or  grooves 
provided  in  the  partition  A,  and  in  the  cylinder  covers. 


Fiy.   402. 


Fig.  403. 


Botary  Engine. 


On  the  other  hand,  however,  the  steam  pressure  acts 
to  press  the  shaft  against  the  sides  of  the  bearing.  The 
wear  of  the  piston  is  greatest  at  the  circumference  of 
the  cylinder  bore,  and  less  as  the  shaft  is  approached, 
which  renders  it  difficult  to  maintain  the  piston  steam- 
tight.  Furthermore,  the  piston  area  is  small  in  propor- 
tion to  the  length  of  the  stroke,  hence  the  loss  of  heat 
from  cylinder  radiation  is  great. 

From  these  causes,  rotary  engines  are  less  economical 
than  reciprocating  or  rotative  engines,  and  therefore 
find  their  field  of  usefulness  confined  to  cases  in  which 
economy  of  fuel  is  not  of  primary  importance 

A  representative  of  rotary  engines  is  given  in    Fig. 


The  ring  is  disposed  eccentrically  to  the  shaft,  and  as 
at  its  highest  point  it  is  in  contact  with  the  cylinder 
between  the  ports  F  and  G,  it  forms  a  constant  abut 
ment  for  the  steam.  The  latter  entering  between  this 
abutment  and  the  piston,  acts  directly  upon  the  piston, 
which  being  merely  a  lever  arm  as  regards  the  shaft,  of 
course  turns  the  same,  traveling  in  the  direction  of  the 
arrow.  In  passing  the  abutment  part  of  the  ring,  the 
flukes  fit  into  a  recess,  so  that  the  contact  between  the 
abutment  and  cylinder  is  always  maintained.  The  re- 
versing gear,  by  which  steam  is  admitted  to  either  port, 
by  means  of  a  common  D  valve-,  is  operated  by  the 
hand  lever  shown. 


332 


MODERN  STEAM  EXGLVES. 


Fig,    404. 


-A 77. }   <  '<,.\.\j-;cn:i>  A.U//.YAX 


404   and  405    represent  an   Engine    in  which 
the  ryiiinlers  are  set  :U  a  riurht  alible,  and  the  pistOn-TOdB 

Keiiig    prolong. I    ].;i>i     tlie    crank  i>ms,    ami    passing 
through  guides,  no  gnid  .  iy. 

Fig.  404  is  a  front,  and  lig.  405  a  plan  view  of  the 


during  each  engine  rovolutioji  in  the  cranks  D  and  0. 

As  the  crank-pins  A  and  0  must  always  move  at 
right  angles  to  each  other,  it  is  evident  that  the  long 
arm  of  the  floating  crank  has  a  very  peculiar  motion. 
Thus,  starting  from  the  positions  A,  B,  and  C  in  the 


405. 


engine.  A  is  a  crank  pin  fast  in  the  crank  C,  which 
carries  a  crank-pin  for  the  other  piston-rod.  This 
crank-pin  has  journal  I  .earing  in  the  crank  cheek 
B,  the  latter  having  a  crank-pin  with  journal  bearing  in 


diagram,  fig.  406,  during  the  first  quarter  revolution,  it 
lies  at  varying  angles  at  the  left  of  the  vertical  lina 
During  the  next  quarter  it  inclines  in  the  opposite  direc- 
tion, and  to  the  right  of  the  vertical  line,  while  during 


Fig.  406. 


the  crank  D,  which  is  fast  upon  the  main  shaft  of  the 
engine.  The  combined  lengths  of  B  and  D  equal  the 
length  of  crank  C,  which  is  half  that  of  the  piston-stroke. 
It  will  be  observed  that  crank  B  is  what  may  be 
termed  a  floating  or  free  crank,  its  two  pins  revolving 


the  third  quarter  the  end  that  was  previously  at  the 
bottom  reaches  the  top,  and  continues  so  during  the  rest 
of  the  stroke.  This  floating  crank  seems  to  revolve  in 
a  direction  opposite  to  that  of  the  main  shaft.  Its  posi- 
tion may  Ha  found  at  any  position  of  the  piston,  by » 


834 


MODERN  STEAM  ENGINES. 


means  of  the  diagram  Fig. -4  00.  Suppose,  for  example, 
that  the  parts  are  in  the  position  shown  in  Fig.  405,  the 
three  crank  cheeks  or  arms  being  then  all  in  line.  The 
black  dots  in  Fig.  406  will  then  represent  the  crank- 
pins,  A  being  the  pin  attached  to  the  outer  piston-rod, 
the  black  dot  at  B  representing  the  inner  pin,  whose 
patli  of  motion  is  the  circle,  and  the  black  dot  at  C  rep- 
resenting the  crank-pin,  for  the  other  piston-rod. 

It  is  obvious  that  the  pin  B  will  always  be  somewhere 


crank-pins  C  B,  fig.  406),  position  B».  Again  suppose 
the  outer  crank-pin  (A  fig.  406)  moves  from  A1  to  A2, 
and  the  middle  pin  (C  fig.  404)  will  have  moved  to  posi- 
tion C8,  and  the  inner  pin  (B  fig.  404)  to  position  B2, 
and  so  on  through  all  the  other  numbered  letters 
similar  numbers  indicating  simultaneous  positions. 
Twelve  positions  are  plotted  on  the  diagram,  and  it  is 
easy  to  follow  the  parts  throughout  the  stroke. 

It  is  obvious,   that  the  cylinders  may  be  placed  in 





Fig.  407, 

on  the  circle,  which  represents  its  path  of  motion,  and 
to  find  its  position  for  any  given  piston  position,  all  we 
require  to  do  is  to  set  a  pair  of  compasses  to  the  radius 
of  crank-pins  A  C,  and  another  pair  to  the  radius  of 
crank  pins  B  0,  and  we  may  trace  the  motion  as  follows: 
Suppose  the  outer  crank-pin  moves  from  A  to  A1,  and 
from  A1  (with  the  radius  of  crank-pins  A  C),  we  may 
mark  at  C1  the  corresponding  position  of  the  crank-pin 
C.  To  find  the  position  crank-pin  B  will  have  moved  to, 
we  mark  from  C1  (with  a  radius  equal  to  that  of  the 


Fig.  408. 

any  required  positions,  so  long  as  their  bores  are  at  a 
right  angle,  and  also  that  in  place  of  two  cylinders,  four 
may  be  used,  two  taking  the  place  of  the  guides  shown 
in  the  illustrations. 

Figs  407  and  408  show  two  cylinders,  one  vertical 
and  the  other  horizontal,  and  it  is  obvious,  that  we  may 
trace  out  the  paths  of  motion,  as  given  above,  by  draw- 
ing the  center  lines  to  represent  the  axial  lines  of  the 
pistons.  The  objection  to  this  class  of  engine  is  the 
excessive  friction  and  wear  of  the  crank-pins. 


Till-'.  STKAM  ROCK   DRILL. 


335 


ROCK-DRILI.INV,   K.XOIXK  OR  ROCK-DRILL. 

Engines    for   piercing  holes    in    rock,    for    receiving 

oaves,  are  called,  in  general  terms.  li,a-h-li,-ili-i.     A 

rock  ilri.  i 'f  a  cylinder  mounted  upon  an  adjus- 

•  •  frame,  that  permits  the  eylinder  to  be  set  in  the 

direction  in  which  the  hole  is  to  lie  ilriilecl. 

Tlie  cvliinler  i»  fed  to  the  cut.  and  the  rate  of  feed  i| 
so  regulated,  that  the  pist>  is  maintained  as 

nearly  as   po/siMe  in  the  same   part  or    length  of    the 
cylinder  '; 

The  valve  is  sometimes  operated  by  tappets  in  connec- 
tion with  the  steam  or  compressed  air  that  drives  the 
rock-drill,  and  at  others  by  the  piston  admitting  steam 
that  operates  the  valve.  Steam  is  used  to  drive  the 
drill  when  it.  is  used  in  the  open  air,  and  compressed 
air  when  the  drilling  is  to  be  done  in  tunnels  or  simi- 
larly confined  places,  or  when  the  boiler  for  generating 
steam  could  not  be  placed  near  enough  to  the  engine  to 
prevent  great  loss  from  condensation  in  the  steam  pipe. 


Tlie  Ingersoll  Eclipse  Bock- Drill. 

In  fig.  409  is  shown  the  Ingersoll  rock-drill  mounted 
upon  a  tripod,  for  surface  work.  As  the  tripod  legs  are 
pivoted  at  their  upper  ends,  it  is  obvious  that  they  may 
be  moved  to  bring  the  drill  into  the  required  position, 
the  weights  serving  to  anchor  them. 

The  drill  is  attached  to  the  piston-rod,  as  shown,  and 
the  feed  is  put  on  by  operating  the  feed  screw,  which 
moves  the  cylinder  down  a  slide  provided  upon  the 
frame. 

A  sectional  view  of  the  cylinder  is  given  in  fig.  410, 
in  which  it  is  seen  that  it  is  provided  with  steam  and 
exhaust  ports  of  the  usual  pattern. 

The  two  dotted  circles  F  P'  represent  open  passages 
in  the  cylinder,  which  are  connected  with  the  exhaust 
port  E,  and  hence  the  interior  of  the  cylinder  between 
F  F'  is  at  all  times  open  to  the  atmosphere.  Now 
observe  the  two  passages  D  D':  These  are  small  brass 
tubes  opening  a  passage  from  the  space  in  the  steam 


chest  at  each  end  of  the  valves,  to  the  interior  of  the 
cylinder  within  the  length  between  F  and  F':  Hence, 
if  there  were  nothing  in  tin;  cylinder  to  shut  the  pas- 
sage D  and  D',  each  end  of  the  valve  would  be  open  to 
the  exhaust;  but  we  have  the  piston  B  moving  back 
and  forth  in  the  cylinder,  and  having  a  stroke  from  X 
to  Y.  This  piston  has  a  long  bearing  in  the  cylinder, 
broken  in  its  center  by  the  annular  space  S  S':  This 
space  is  a  constriction  in  the  diameter  of  the  piston,  and 
makes  an  open  space  or  chamber  all  around  it.  The 
length  of  this  space  is  such  that,  wherever  the  piston 
may  be  in  the  cylinder,  this  space  is  at  all  times  open  to 
one  of  the  passages  D  D',  and  hence  to  one  of  the 
holes  F  F',  which  leads  by  way  of  the  exhaust  port  E, 
to  the  open  air.  S  S',  therefore,  is  an  exhaust  chamber 
carried  up  and  down  with  the  piston.  This  exhaust 
chamber  can  never  be  open  to  both  of  the  passages  at 
D  D'  at  the  same  time.  When  the  piston  is  on  the  up 
>t  ]•(  ike  it  is  open  to  one  of  these  passages,  and  when  on 
the  down  stroke,  to  the  other.  The  valve  is  spool- 
sJuiped,  and  has  a  hole  through  its  longitudinal  axis, 
through  which  passes  the  bolt  T,  which  serves  to  guide 
the  valve  in  its  motion  back  and  forth,  and  which,  by 
means  of  a  spline,  prevents  its  rolling  on  its  seat.  In 
the  bottom  of  the  steam  chest  there  are  two  cored  pas- 
sages, connecting  the  tubes  D  and  D'  with  the  ends  R' 
and  R  of  the  valve.  These  passages  cross  each  other, 
so  that  R  is  connected  with  D',  and  R'  with  D. 

In  the  figure  the  piston  has  completed  the  up  stroke; 
the  valve  has  been  reversed;  and  the  drill  is  ready  to 
strike  a  blow.  Suppose  the  steam  to  be  admitted 
through  the  chest  to  the  valve  at  a  point-say  O.  As 
the  spaces  at  0,  N  and  N'  are  in  one,  the  steam  will 
encircle  the  valve,  bearing  it  down  upon  its  seat  through 
the  excess  of  pressure  at  0.  Escaping  over  the  top  of 
the  valve  flange  it  will  also  occupy  R';  this  being  con- 
nected with  D,  and  D  being  closed  by  the  lower  piston 
head,  there  is  no  outlet.  Now  R  being  connected  with 
D',  and  as  D'  is  now  open  to  the  piston  exhaust  cham- 
ber, the  space  behind  the  valve  flange  at  R  is  free  to 
the  exhaust,  and  hence  the  steam  pressure  in  R'  holds 
the  valve  close  at  R,  so  long  as  D'  is  open  to  the  piston 
exhaust  passage.  Therefore  the  valve  must  remain  in 
its  present  position  until  the  piston  moves.  The  port  P 
being  open  to  the  live  steam  chamber  in  the  valve,  and 


MODERN  STEAM  ENGINES. 


Fig.  409. 

Ingersoll's  Eclipse  Bock-Drill. 


TIH-:  >•/'/•;.!. 


337 


the  }>ort,  I'  to  the  exhaust,  tho  steam  vmirh  I" 

into  tin-  cylinder  at  M,  ami  pressinir  upon  the  hack  of 
the  piston  drives  it,  down.  As  ti.e  K.-TOII  move-  down 
"11  exhaust  ]>as-ai:e  is  o;.eii  to  I),  and  at  the 
saint!  inslani  1 1'  is  shu!  olT  1>y  the  ii]>j>er  j.i.-ion  liead. 
The  result  isiha:  I >  i>  suddenly  opened  to  the  atmos- 
phere, and  the  chanioer  II'  l.eiii'j;  connected  \vi;h  it.  is 
exhausted.  The  live  steam  around  tin 
towards  this  exhaust  opening,  e.-irryinir  the  valve  with  it 
ami  pressing  it  against  the  upper  hea<l  of  the  chest  at 


J-'i;/.   411. 

R',  thus  the  valve  is  reversed,  the  machine  exhausts,  and 
the  motion  of  tile  piston  ia  reversed. 

We  here  have  an  intermittent  and  reciprocative 
action  of  piston  and  valve,  one  being  dependent  upon 
and  regulated  by  the  other,  yet  each  is  separate,  and 
removed  from  the  other,  and  without  direct  mechanical 
connection.  The  valve  of  this  feature  in  Rock  Drill- 
ing Machinery  is  evident.  Where  a  piston  is  made  to 
strike  rock  at  the  rate  of  three  hundred  blows  a  minute, 
it  is  important  that  it  should  move  freely  in  its  cylinder 
and  that  it  should  strike  nothing  but  the  rock. 

By  simply  feeding  down  the  cylinder,  the  piston  will 


OF  THE 

UNIVERSITY) 


338 


MODERN  STEAM  EXGL\KS. 


work  entirely  in  the  upper  part,  cutting  off  so  roon  as 
the  blow  is  delivered,  and  increasing  its  stroke  as  the 
hole  is  driven.  This  is  important,  especially  in  starting 
or  pointing  holes. 

Fig.  .411  illustrates  the  manner  in  which  the  drill 
is  revolved  a  certain  amount  during  each  upward  pis- 
ton-stroke. Within  the  upper  end  of  the  piston  is  a 
bar  with  twist  grooves,  and  fitting  to  the  same  is  a  nut; 
fast  in  the  head  of  the  piston  is  a  ratchet  wheel  having 
two  pawls,  which  permit  of  the  ratchet  wheel  revolving 
in  one  direction  only.  When  the  piston  makes  an  up- 
ward stroke,  the  spirals  cause  it  to  make  a  part  of  a 
revolution,  and  the  pawls  fall  into  the  ratchet  teeth, 
preventing  the  spiral  bar  from  turning  back  to  the  same 
place. 

By  using  two  pawls  the  teeth  of  the  ratchet  may  be 
made  twice  as  coarse,  and  therefore  twice  as  strong  for 
a  given  pitch  of  ratchet,  because  the  ratchet  wheel 
needs  to  move  bnt  half  the  pitch  of  the  ratchet,  in 
order  to  permit  one  or  the  other  of  the  pawls  to  engage. 

The  piston  diameter  varies  from  If  inches  to  5  inches 
in  diameter,  the  larger  sizes  being  used  for  deep  holes. 

It  is  found  that  vertical  holes  may  be  drilled  one- 
quarter  faster  than  horizontal,  the  rate  of  feed  being 
diminished  in  proportion  as  the  rock  is  either  hard  or 
seamy. 


The  Ingersoll  Air  Compressor. 


The  construction  of  the  Ingersoll  air  compressor  for 
driving  rock-drills  is  shown  in  Figs.  412,  413,  414 
and  415. 

It  consists  of  a  steam  and  air  cylinder,  whose  pistons 
are  in  line,  and  connect  to  a  cross-head  C,  operating  in 
the  guides  G,  the  connecting-rods  being  connected  out- 
side the  guides.  It  is  obvious,  that  the  pressure  in  the 
air  cylinder  increases  as  the  air  piston  approaches  the 
end  of  the  stroke,  at  which  time  the  steam  piston  has 
the  least  pressure,  because  of  the  cut-off  and  release 
occurring  before  it  completes  its  stroke. 

This  necessitates  the  employment  of  heavy  fly-wheels 
W,  which  store  up  the  power  received  during  the  ear- 


lier part  of  the  stroke,  and  deliver  it  back  again  at  the 
later  part. 

The  air  cylinder  is  provided  with  a  pump,  by  which 
water  is  forced  into  the  cylinder  and  mingled  with  the 
air,  thus  keeping  it  cool  and  preventing  its  expansion 
from  the  heat,  that  would  otherwise  be  generated  dur- 
ing its  compression,  it  being  obvious  that  such  heating 
and  expansion  would  increase  the  load  on  the  engine, 
and  diminish  the  quantity  of  air  compressed. 

The  power  of  the  engine  is  proportioned  to  the 
amount  of  its  load,  by  means  of  a  Meyer's  cut-off  valve, 
the  eccentrics  operating  rock-shafts  c  c,  which,  at  their 
upper  ends,  operate  the  valve  rods,  that  for  the  cut-off 
valve  being  seen  at  f. 

The  cut-off  valves  are  moved  to  vary  the  point  of 
cut-off  by  a  right  and  left  hand  screw,  operated  by  a 
hand  wheel  shown  at  J. 

To  maintain  the  required  pressure  in  the  receiver  in 
which  the  compressed  air  is  stored,  and  to  maintain  the 
pressure  uniform,  the  following  construction  is  employ- 
ed: The  cross-head  C  drives  a  lever  A,  which  is  pivoted 
at  one  end,  and  which  operates  the;  pump  rod  r,  the 
pump  being  on  the  side  of  the  air  cylinder.  The 
pump  discharges  alternately  into  each  end  of  the  cylin- 
der through  discharge  pipes,  which  may  be  placed  in 
communication  or  separated  by  a  valve. 

The  suction  pipe  is  also  provided  with  a  valve,  and 
the  mechanism  is  such,  that  when  the  air  pressure  in  the 
receiver  begins  to  increase  above  that  required,  a  piston 
closes  the  suction  pipe  and  opens  communication  between 
the  two  delivery  passages,  so  that  the  water  already  in 
the  air  cylinder  passes  through  the  delivery  pipes,  from 
one  side  to  the  other  of  the  air  piston.  At  the  same 
time  a  valve  in  the  admission  pipe  of  the  steam  cylin- 
der is  closed,  thus  diminishing  the  steam  supply,  and 
therefore  the  engine  speed. 

A  further  feature  of  this  part  of  the  mechanism 
as  applied  to  the  larger  sizes  of  compressors,  is  that 
the  compressed  air  in  the  receiver  may  be  utilized  for 
starting  the  engine,  the  construction  being  as  follows,: 
Fig.  414  is  a  side  view  of  the  air  cylinder  shown 
removed  from  the  engine,  and  broken  away  at  one  end 
to  expose  the  valves  and  the  delivery  passage  d,  the 
regulating  mechanism  being  shown  in  section;  and  fig. 
415  is  an  end  view  of  the  same. 


Tin-:  /.  u, •/:/;>•  o/./.  AH: 


339 


340 


MODERN  STEAM  EXG1XES. 


THE  L\<;l-:i!S<>l.L   AIR    C 


341 


The  Ingersoll  Air  Compressor,  —  The  Governing  Mechanism. 


-'i'n.    415. 


342 


MODERN  STEAM  ENGINES. 


Referring  to  these  two  views,  a  pipe  from  the 
receiver  admits  the  compressed  air  into  the  chamber 
a  a,  and  also  beneath  the  small  piston  P,  which  is  held 
down  by  the  weight  shown  attached  to  the  end  of  lever 
L,  hence  this  corresponds  to  a  common  safety  valve, 
except  that  the  raising  of  the  piston  does  not  permit 
the  compressed  air  to  escape.  The  weight  is  adjusted 
in  amount  to  suit  the  pressure  to  be  maintained  in  the 
receiver.  Xow  suppose  that  from  a  rock-drill  being 
stopped,  or  from  some  other  ordinary  cause,  the  pres- 
sure in  the  receiver  begins  to  increase,  and  piston  P  will 
be  raised,  and  this  will  lift  the  valve  v,  which  is  on  the 
same  rod  as  piston  P.  When  valve  v  is  raised  the  two 
delivery  passages  d  d'  of  the  pump  (which  both  commu- 
nicate with  the  chambers  e  e')  are  in  open  communica- 
tion, and  the  water  on  the  delivery  side  of  the  pump 
passes,  as  tiie  air  piston  reciprocates,  to  and  fro  in  the 
delivery  passages  d'  d,  from  one  end  to  the  other  of  the 
air  cylinder.  From  the  time  that  the  piston  P  begins 
to  close,  the  water  supply  to  the  pump  begins  to  dimin- 
ish, because  the  tappets  T  on  the  rod  suspending  the 
weight,  meets  the  valve  stem  of  globe  valve  G  and 
closes  that  valve. 

Simultaneously,  with  this  action  a  second  one  occurs, 
inasmuch  as  that  the  lever  L,  as  it  rises,  meets  a  bell 
crank  M.  which  operates  the  rod  R.  and  this  closes  the 
steam  governor  valve  V,  dimishing  the  supply  of  steam 
to  the  steam  cylinder.  All  these  regulating  devices, 
therefore,  are  operated  by  the  motion  of  the  piston  P. 
which  is  determined  by  the  pressure  in  the  receiver, 
and  is,  therefore,  automatic. 

Now  suppose  the  engine  to  have  been  stopped,  its 
steam  supply  being  shut  off,  and  to  start  it  again  the 
steam  is  turned  on  again,  and  the  compressed  air  in  the 
receiver  may  be  utilized  to  assist  in  starting,  by  the 
following  construction.  The  annular  chamber  a  a, 
being  in  open  communication  with  the  receiver,  is  filled 
with  compressed  air,  which  is  excluded  from  the  cham- 
bers e  e',  by  valves,  whose  operating  hand  wheels  are 
shown  at  H  and  A  respectively.  If,  however,  the  air 
piston  is  at  the  right  hand  end  of  the  cylinder,  valve  h 
may  be  opened,  admitting  the  compressed  air  into 
chamber  e',  from  which  it  will  pass  through  d'  into  the 
right  hand  end  of  the  air  cylinder,  and  thus  aid  in  pro- 
pelling the  piston. 


Similarly   if  the  piston  is  at    the    other    end    of  the 
cylinder,  valve  H  may  be  operated   to  admit  air  from 
a  through  e  to  rf,  to  propel  the  air    piston,  the   valve 
being  closed  as  soon  as  the    engine  is    fairly    started. 
Obviously,  in  operating  either  of  these  valves,  the  direc 
tion  of  engine  revolution  is  to  be  considered,  since  it 
determines  which   valve  must  be  opened;    at  g  and  g' 
are  glands  to  close  communication  between  the  small 
cylinder  P  and  the  chamber  e'. 


TJie  Knowles  Steam  Pump. 


Fig  41H  is  a  general  and  fig.  417  a  sectional  view  of 
the  Knowles  steam  pump,  whose  construction  is  as  fol- 
lows: The  steam  and  water  pistons  are  in  line,  and  arc 
connected  by  a  piston-rod,  to  which  is  attached  an  arm 
A.  Upon  this  arm  is  a  roller  having  contact  with  the 
bottom  edge  of  the  rocker  bar  T,  which  is  pivoted  at  its 
center,  this  bottom  edge  being  curved,  so  that  as  the 
arm  A  traverses,  it  alternately  lifts  one  or  the  other  end 
of  the  rocker  bar. 

At  B  is  a  link  attached  to  a  short  arm  on  the  rod  D, 
so  that  as  A  traverses  to  and  fro,  the  vertical  vibration 
its  roller  gives  to  rocker  arm  T,  causes  B  to  slightly 
revolve  the  rod  D  of  the  chest  piston,  and  this  causes 
the  chest  piston  to  operate  the  main  B  shaped  valve,  by 
reason  of  the  following  construction:  At  each  end  of 
the  steam  chest  piston,  is  a  small  port,  one  of  which  is 
shown  at  the  right  hand  end  of  the  chest  piston.  Near 
each  end  of  the  seat  of  the  steam  chest  piston  is  a  small 
steam  and  exhaust  port,  which  are  opened  and  closed 
by  motion  of  the  chest  piston,  and  alternately  admit 
steam  to,  and  exhaust  it  from  the  ends  of  the  chest  pis- 
ton, and  thus  operate  it  endwise. 

At  v  and  v'  are  tappets  that  while  not  absolutely 
essential  to  the  valve  motion,  serve  as  safeguards  to 
move  the  chest  piston,  should  the  rotary  motion  of  the 
chest  fail  to  do  so. 

Referring  now  to  the  water  cylinder,  the  two  lower 
valves  are  for  the  suction,  and  the  two  upper  for  the 
delivery,  as  the  pump  piston  is  shown  moving  to  the 
left,  the  right  hand  side  is  drawing,  hence  the  right 
hand  suction  valve  is  open,  while  the  left  hand  delivery 


Tin-:  >yv-:.u/ 


Figs.  416.   &  417. 
Knowles  Steam  Pump. 


344 


MODERN  STEAM  ENGINES. 


valve  is  also  open,  to  permit  the  escape  of  the  water  on 
the  left  hand  side  of  the  water  piston.  The  left  hand 
suction  valve  is  closed,  and  held  closed  by  a  spiral 
spring  on  its  back,  as  well  as  by  the  pressure  of  the 


operated  from  the  piston-rod  of  the  other,  as  was  fully 
explained  with  reference  to  fig.  373  of  the  Worthington 
Compound  Condensing  Engine. 

When  the  circumstances  render  it  necessary  to  use  the 


-•- 


delivery,  while  the  right  hand  delivery  valve  is  similarly 
held  closed  by  its  spring,  and  by  the  pressure  of  the 
delivery,  as  well  as  by  the  suction. 


The  Worthington  Steam  Pump. 


A  general  view  of  a  Worthington  Steam  I'ump  is  in 
fig.  418.  It  consists  of  a  pair  of  steam  cylinders  and 
pumps  connected  together,  so  as  to  form  virtually  one 
machine.  The  valve  gear  for  one  steam  cylinder  is 


steam  expansively,  compound  steam  cylinders  are  em- 
ployed, the  arrangement  being  shown  in  fig.  419.  The 
valve  motion  is  the  same  as  befoi-e,  except  that  the  valve 
rod  T  passes  through  the  low  pressure  steam  chest,  to 
the  high  pressure  steam  chest,  both  valves  being  worked 
by  one  rod.  The  exhaust  from  the  high  pressure 
cylinder  passes  through  the  pipes  shown  direct  to  the 
low  pressure  steam  chest. 

Figs.  420  and  421  show  the  construction  as  applied 
to  pumps  for  brewery  purposes,  in  which  thick  liquids 
require  to  be  pumped.  This  suction  chamber  is  at  S, 
:uul  a  piston,  instead  of  the  usual  plunger,  is  employed, 


TIIK  >T/:.M/ 


345 


Fig.  419. 
Worthiington  Steam  Pump. 


346 


MODERN  STEAM 


so  as  to  reduce  the  clearance  to  a  minimum,  the  lower 
pair  of  valves  r'  r-,  are  obviously  for  the  suction,  and 
the  upper  pair  v3  and  r*  for  the  delivery.  The  suction 
chamber  S  is  common  to  both  pumps,  and  as  one  or  the 
other  of  the  suction  and  of  the  delivery  valves  are  always 
open,  the  suction  and  delivery  streams  are  continuous. 
The  steam  valve  motion  is  constructed  as  follows: 


move  until  it  covers  the  exhaust  port  e,  the  steam  re- 
maining in  the  cylinder  being  compressed,  and  finally 
cau.sing  the  piston  to  pause  at  the  end  of  its  stroke. 
During  this  pause  the  suction  valve  v'  and  the  delivery 
valve  v3  will  quietly  seat  themselves  without  inducing 
reverse  currents  in  either  the  suction  or  delivery  pipes, 
as  occurs  when  the  valves  close  quickly.  The  admis- 


Fiy.  4 'JO. 
The  Worthington  Pump  as  Applied  to  Brewery  Purposes, 


Two  arms  A  and  B,  receive  motion  from  the  respective 
piston-rods,  the  arm  on  the  left  hand  engine  operating 
the  valve  for  the  right  hand  one.  Thus  arm  A  oper- 
ates a  rock-shaft  B,  connected  to  the  valve  rod  R,  whose 
block  v,  that  fits  in  the  valve,  lias  a  certain  amount- of 
lost  motion  or  play.  Now  suppose  motion  to  occur  in 

the  direction  of  the  arrows,  and  the  steam  piston  P  will 
40 


sion  of  steam  for  the  next  stroke  of  piston  P,  is  so 
regulated  that  it  first  permits  of  this  pause,  and  then 
drives  the  piston  on  the  return  stroke.  The  lost  motion 
between  the  blocks  v  and  the  valve,  is  so  regulated  in 
amount,  that  one  piston  takes  up  the  motion  just  before 
the  other  pauses,  hence  a  steady  and  continuous  flow  of 
water  is  maintained. 


THE  STK.iM  IT  MI'. 


347 


TJie  Gordon 

Isocliroiml 


Mu.  \-n-ett 

l:iii>ine. 


Fig.  422  represents  the  (Jin-don   ami   Maxwell    Isoch- 
ronal steam  pump.  in  which    a   cataract,    is    employed  to 

govern  and  equalize  the  pump  motion.     Live  steam   is 

admitted  l>y  the  valve  F  tc>  the.  chamber  K  K',  in  which 


g  fast  upon  the  rod  D"  of  the  valve  mov- 
ing piston. 

Wi'.'ii  the  steam  piston  B  is  at  the  end  of  its  stroke, 
and  the.  ports  are  in  the  position  shown  in  the  figure, 
the  valve  F  has  admitted  steam  which  acts  against  the 
end  face  at  E'  of  the  vulvo  moving  piston  D,  and  as 
the  port  a'  is  closed,  and  the  piston  B  and  cataract 
cylinder  at  rest,  the  valve  moving  piston  will  move  to 
the  left,  and  operate  the  main  valve  to  open  port  a'. 


n;i.  421. 
Sectional  View  of  the  Worthington  Pump  as  Applied  to  Brewery  Purposes. 


the  piston  valve  D  D'  operates.  This  valve  moving 
piston  operates  the  valve  for  the  ports  a  a'  of  the  main 
cylinder  A.  The  cataract  cylinder  H  is  filled  with  oil, 
and  is  given  a  positive  motion  through  the  medium  of 
arm  J,  link.  L",  lever  I,  an. 1  .rod  I',  the  cataract  or  oil 


Between  the  point  at  which  the  valve  piston  begins 
to  move,  and  that  at  which  the  valve  opens  the  port  a' 
a  certain  period  of  time  must  elapse,  during  which  the 
piston  B  pauses,  which  gives  fime  for  the  delivery 
valves  of  the  pump  to  close  quietly.  This  period  of 


348 


MODERN  STEAM  ENGINES. 

fiafc  /f^  ,/y  AO*  «*i 

^ 


I 


tJ 

S 
g 


Till-'.  KTKAM   ITMP. 


349 


<>y  the  niiiin    valve   having  >oWn 

in   J  •'•'"g 

piston  D  will   move   tlie   main    \  .e   amouii 

the  steam  hip.  ]«•;>  to  open.      Suj 

a'  to  In;  open  mid  1>  t"  move  lo  tin-  left,  ami  the  catar- 
act  cylinder  II  will  !•<•  moved  to  the  right,  while  its 
jiiston  will  stand  still.  The  aitiount,  of  pre  —  ure  at  K' 
acting  to  im  piston  valve  1>  to  the  left,  will 

remain  coin-taut  so  long  an  the  valve  K  admit*  steam  to 
K'.  Hut  the  amount  of  counteracting  pressure  on  the 

face  of  the  oil  or  cataract  piston  <<.  will  vary  with  the 
effort  of  tht-  catawt  or  oil  cylinder  II,  to  move  to  the 
right,  and  when  this  effort  places,  upon  the  face  of  the 
oil  piston,  a  pressure  exceeding  that  of  the  steam  pres- 


>ure  im  I),  then  the  piston  (1  will  move  to  the  right  (in 
lie  same  direction  as  II)  carrying  tiie    piston  and    main 

valve  over  the  main  steam  port,  and  reducing,  or  cut- 
iinLf  olT,  as  the  ruse  may  lie,  the.  supply  of  steam  to 
pistun  1!.  Now  suppose  that  from  BOIIU-  cause  or  other, 
HOB  to  the  pump  plunger  i«  suddenly  relaxed, 
or  diminished,  and  piston  B  will  accelerate  its  speed. 
:i'ort.  will  lie  communicated  to  the  oil  cylinder  H; 
but  the  diminished  opening  at  L  will  not  permit  the  oil 
to  puss  freely  through  to  the  other  side  of  G,  hence 
the  pressure  in  11  will  cause  G  to  move  to  the  right 
in  unison  with  the  oil  cylinder,  thus  mpving  D  to  the 
right,  reducing  the  steam  supply  to  port  a',  and  propor- 
tioning it  to  the  resistance  offered  to  the  pump  piston. 


INDEX. 


Adjustable  cut-off  engine.  13 

engines.  ltis-137 
Admission,  findin.!:  the  point  of,  45.  143 

of  the  Reynolds-Corliss  engine.  '2'2,'>-'2'2~ 
valve  of  the  I'urter-Allcn  engine.  149 

various  positions  of  the, 

149 

Advance,  angular,  definition  of.  17,  18 
Air  compressor,  Inger>oll'.-.  :;:;s-342 

governing  iiiL'chanisiii  of  the.  34n,  341 
side  elevation  and  plan  of,  339 
Allen  valve.  2S-32 

n instruction  and  various  positions  of  the,  during  a 

revolution.  US,  L".i 

diagram  of  the  port  openings  of  the,  31,  32 
increase  of  lead  with  the,  85,  86 
link  iimtiiin  with  the.  s-1-86 
American  locomotives,  link  motion  used  on,  89 

passenger  locomotives,  diagram  of  the  port  openings  of 

a  valve  motion  of,  26,  27 
Angular  advance,  definition  of,  17,  18 
of  eccentric,  28 
variation  in  the  amount  of.  '2'2 
Angularity  of  the  connecting  rod.  20,  21,  26 

of  the  valve-rod,  effect  of  the,  36 
Arniington-Sinis  engine,  175-183 
Automatic  cut-off  engine,  13 

advantages  of  the,  144 
engines,  144-238 
classes  of,  144 


Ball  automatic  cut-off  engine,  214-216 

Beam  engines,  11 

Boiler  efficiencies  during  the  trial  of  the  engines  of  the  S.  S. 

Meteor,  302 

of  Prick's  traction  engine,  315 
Boilers  of  the  S.  S.  Meteor,  298 
Brewery  purposes,  Worthington's  steam  pump  as  applied  to, 

344-346 

Bridges,  definition  of  the,  15 
Buckeye-engine,  160-174 

Bulkley's  independent  injector  condenser,  254,  255 
injector  condenser,  245-248 

application  of  the,  247 

as  arranged  for  natural  water  supply,  249 


Classification  of  steam  engines,  11-32 

Clearance  in  a  valve.  19 

Coal  consumption,  diagram  of  the,  in  testing  the  engines  of 

the  S.  S.  Meteor.  297.  299 
measurement  of,   for  testing  the  engines  of  the  S.  S. 

Meteor,  298,  299 
Scotch,  analysis  of,  299 
Col  well' s  engine  for  sugar  mills.  321-323 
Common  slide  valve  engine,  11-32 
Compound  condensing  and  triple  expansion  stationary  engines, 

260-274 
engine,  11 
marine  engine,  example  of  a,  276 

for  an  ocean-going  steamship,  279- 

281 

engine,  11,  239-242 

Compression  and  lead,  equalizing  of,  41 
or  cushioning,  17 
regulation  of,  in  the  Wheelock  automatic  cut-off  engine, 

236 
Condenser,  Reynolds',  255-259 

construction  of,  259 
sectional  view  of,  257 
top  view  partly  in  section  of,  258 
Condensers,  classification  of,  244 
Condensing  engine,  1 1 ,  244-259 
Connecting  rod,  angularity  of  the,  20,  21,  26 

dispensing  with  the,  54 
Corliss  automatic  cut-off  engine,  221-236 
Crank  and  eccentric,  relative  amount  of,  35 
tracing  the  movements  of,  35 
piston,  relative  motion  of.  34 
of  the  Porter-Allen  engine,  finding  the  position  of  the, 

when  the  valves  are  set,  1 52 
pin,  effect  of  variation  between  the  position  of  the,  and 

that  of  the  piston,  36 
path  of  the,  34 

position  at  the  shortest  point  of  cut-off,  to  find  the,  137 
shaft,  varying  the  point  of  cut-off  by  shifting  the  eccen- 
tric across  the,  138-143 
to  find  the  position  of  the,  at  the  time  the  main  valve 

would  cut-off,  122 
link  corresponding  to  that  of 

the,  92 

Crossed  rods,  equalizing  the  lead  with,  83,  84 
link  motion  with,  82-84 

(351) 


352 


INDEX. 


Crossed  rods,  variation  of  lead  in,  S3 

Cut-off  eccentric,  diagrams  for  finding  the  position  of  the, 

125,  130 
limits  within  which  the  position  of  the,  may  be 

varied,  113,  114 
the  position  of  the,  113-120 
engine,  13 

automatic,  advantages  of  the,  144 
engines,  adjustable,  108-137 
automatic,  144-238 
classes  of,  144 
equalizing  the  points  of,  39 

in  the  Wheelock  automatic  cut-off  en- 
gine, 23C>,  237 
point  of  the,  bv  uiakine  the  steam   ports 

of  different  widths,  98-101 
evils  of  a  fixed  point  of,  144.  145 

longest  and  shortest  points  of,  diagrams  of  the  port  open- 
ings for  the,  135,  136 
Meyer's,  108 
point  of,  1 5 
points  of,  equalizing  the,  96-98 

to  equalize,  114-120 
shortest  point  of,  to  find  the  crank  position  at  the,  137 

to  find  the  path  of  the  eccentric  for  the,  1 35 
to  find   the   amount   of  steam   port  opening  for  each 

point  of,  142,  143 
earliest  point  of,  135 
limits  of  the  range  of,  1 35-1 37 

valve  diagram  for  finding  the  position  of  the  cut-off  ec- 
centric, 121 

operating  on  a  fixed  seat,  134 
valves,  action  of.  110-115 

diagrams  of  port  openings  of,   112,  114,  117,  118, 

119,  120,  124,  125,  126,  130,  131,  132,  133 
finding  the  port  opening  for  a  given  point  of,  141, 

142 

riding,  108-137 
setting,  123 

to  find  the  amount  of  lap  for  the,  123 
varying  the  points  of  cut-off,  by  moving  the,  120- 

134 
point  of,  by  shifting  the  eccentric  across  the 

crank  shaft,  138-143 
Cushioning  or  compression,  17 
Cylinder  and  valve  of  the  Armington-Sims  engine,  section 

through  the,  177_ 
straight-line      engine,     horizontal 

section  through  the,  185 
valves  of  the  Buckeye  engine,  cross-section  of,  166 

Porter- Allen  engine,  148-150 

of  the  straight-line  engine,  vertical  section  through  the, 
186 

Dash-pot  of  the  Wheelock  automatic  cut-off  engine,  construc- 
tion of  the,  236 

Dexter  automatic  cut-off  engine,  217-220 
Diagram,  construction  of  the,  24 

form  of.  employed  by  Mr.  ,1.  W.  Thompson  of  the  Buck- 
eye Engine  Works,  38 
from  a  valve  haying  over-travel,  26 
manner  of  obtaining  the  curved  lines  in  the,  24,  25 


Diagram  of  a  cut-off  valve  for  finding  the  position  of  the  cut- 
off eccentric.  121 
coal  consumption  in  testing  the  engines  of  the  S. 

S.  Meteor.  297.  299 
speed   regulation  and    the    use  of   the    auxiliary 

springs  of  the  Buckeye  engine,  174 
the  action  of  a  valve  having  lap,  25 
no  lap,  24 
port  openings  in  the  Porter-Allen  engine,  156, 

157 

of  an  Allen  valve,  31,  32 
Zeuner's  valve,  42-63 

remedy  for  defects  of,  59 

Diagrams  for  designing  valve  motions  or  mechanisms,  33-63 
finding  the  position  of  the  cut-off  eccentric,  125, 

130 
from  a  triple  expansion  stationary  engine,  273,  274 

the  Allen  and  common  valves,  comparison  of,  30 
of  general  conditions  in  testing  the  engines  of  the  S.  S. 

Meteor,  297,  300 
port  openings  given  by  Stephenson's  open  rod   link 

motion,  76,  77 

the  Allen  valve  with  link  motion, 
_  84,  85,  86 

in  the  Armington-Sims  engine,  182,  183 
of  cut-off  valves.   112,   114,  117,  118,   119, 

120,  124,  125,  126,  130,  131,  132,  133 
of  the  Buckeye  engine.  171 
steam  distribution,  24-27 
the  mean  effective  pressures  during  the  trial  of  the 

engines  of  the  S.  S.  Meteor,  297,  300.  301 
the   port    openings   for  the   longest  and  the  shortest 

points  of  cut-off,  135,  136 
principles  involved  in  the  construction  of,  33 
showing  the  steam  distribution,  114 
Direct  acting  engine^,  1 1 
Direction,  definition  of  the  word.  17 
Directly  connected  engines,  333,  334 
Douglass's  valve  gear,  marine  engine  with,  286 

Eccentric,  amount  of  angular  advance  required  by  an,  18 
angular  advance  of,  28 
center  of  the  bore  of  an,  17 

to  find  the,  35 
construction  in  the  Ball  automatic  cut-off  engine,  215, 

216 

cut-off,  diagrams  for  finding  the  position  of  the,  125 
limits  within  which   the  position  of  the,  may  be 

varied.  113,  114 
the  position  of  the,  113-120 
finding  the  path  of  the,  for  the  shortest  cut-off,  1 35 

position  of  the,  in  the  Armington-Sims  engine, 

179-181 
lead,  22 

main,  to  find  the  throw  of  the,  132 
path  of  motion  of  the  center  of  an,  33 
position,  to  find  the  piston  position  for  a  given,  141,  142 
rocker  and  valve  movements  of  the  straignt-line  engine, 

191,  192 

rod,  paths  of  motion  of  the,  74 
shiftable,  138-141 
throw  of  an,  definition  of  the,  17 


INDEX. 


353 


Eccentric,  varying  the  point  of  cut-off,  by  shifting  the,  across 

the  crank  shaft.    i.;- 
Eeceritric.s.  tn  tind  the  position  of  the,  90,  91 

locate  the  po.-itions  of  the,  for  any  point  of  cut- 

.,«'.   IL'T 

Ejector  oondenaer,  244 

Engine',  adjustable  cutoff.   1:1 
A  nn  i  n  ir(  on  -Sims.  175- 1  S3 
automatic  cut  off,  13 

advantage  of  the,  144 
Ball  automatic  cut-off,  1J14-2I6 
Huekeyo,  lfi(»-174 
Colwoll's.  lor  su-ar  mills.  321-323 
common  glide  valve.   I  I-3J 
compound.  II.  23'.i-242 

condensing,  1 1 
condensing.  1 1 .  244-259 
Corliss  automatic  cut  off,  '2-  1-236 
cut-off'.   \\\ 

Dexter  automatic  cut-off,  2 1  7-22(1 
i-fficicncies  during  tho  trial  of  the  engines  of  the  S.  S. 

Meteor.  3d2 

Farcot's  compound.  241-243 
Fishkill.  23l-2:;:i 

(ireene  automatic  cut  off.  230,  231 
Harris-Corliss,  231 
high  prosiire.  1 1 

hoisting  L'ear  for  reversing  on  a,  103 
horizontal  stationary,  construction  of  a,  13,  14 
Idc.   l%-2<>5 
inverted  cylinder.  I .'! 
James  and  \\ardrope,  211,  212 
marine.  275-31  1 

Maxwell  and  Cordon  isochronal  pumping,  347-349 
multi-cylinder,  211.  212 
Ncw  York  Safety  Steam  Power  (jo's.,  214 
portable.  31X-327 
Porter  Allen.  145-160 

prominent  features  in  the  design  of  the,  145 
quadruple  expansion.  307,  .'in*.  300-811 
reversible  rolling  mill,  treat-  for  reversing  on  an,  103 
Robertson's  semi-rotary.  32'.' 
rock  drilling,  or  rock  drill.  :::;:>-338 
rotary.  329-334 
Mini-portable,  h\-  the  Lidgerwood  Maanfaotortng  Co., 

319 

lemi-rotart,  difficulty  in  the.  32H 

speed  of  the  Reynolds-Corliss  engine,  varying  the,  229 
steam,  various  applications  of  the,  312-349 
straight-lino.  ls.-,-l% 
throttling,  13 
traction,  812-321 
triple-expansion.  23'.» 

stationary,  with  cylinders  one  above  the  other, 

270-274 
Twiss.  237.  288 

vertical  compound  condensing,  265,  2f>6 
WestiiiL'house.  L'iir,-L'l  I 
\Vheelock  automatic  cut-off.  234-237 
Wor<hington  compound  condensing,  260-264 
Engines,  adjustable  cut -off,  108-137 
automatic  cut-off,  144-238 


Engines,  automatic  cut-off,  classes  of,  144 
beam ,  1 1 
direct  acting,  1 1 
directly  connected,  333,  334 
hoisting,  .'S27-329 
horizontal,  1 1 
inclined,  11 
marine.  1 1 

varieties  of,  275 
multi  cylinder.  13 
of  the  S.  S.  Mariposa.  287,  288,  290 

Meteor,  298,  294,  295,  296,298 

test  of  the,  296-309 
steam  yacht  Mira,  287,  291,  292 
oscillating.  I  1 
rotary,  13 
semi-rotary.  l:i 
.-ide  lever,  I  I 
stationary,  1 1 

compound  condensing  and  triple  expanding,  260- 

274 

methods  of  compounding  in,  239-24' 
tandotu,  13 
traction.   I  I 
triple  expansion,  examples  of.   2S5-309 

stationary.  L'i'.(i-274 
vertical.  II 
Exhaust  edges.  15 

lap  of  a  valve,  operation  of  the,  18 
means  of  remedying  defects  in  the,  26 
port.   14 
Expansion  of  steam.  27,  28 

to  find  the  total  range  of.  241 

Farcot's  compound  engine,  241-243 

Feed  water,  measurement  of,  in  testing  the  engines  of  the 

S.  S.  Meteor.  299.  300 

temperature  and  consumption  of,   in  testing  the  en- 
gines of  the  S.  S.  Meteor,  301 
Fire  engine,  steam,  325-327 
Fishkill  engine,  231-233 
Frame  and  rocker  of  the  Buckeye  engine,   cross  section 

through  the.  168 
Prick's  portable  engine,  319 
traction  engine.  312-318 
Friction  drum,  Mundy's.  327.  32S 
i  Fuel  used  in  testing  the  engines  of  the  S.  S.  Meteor,  300, 

301 
Furnace  gases,  analysis  of.  300.  301 

temperature  of.  in  testing  the  engines  of  the  S.  S. 
Meteor,  29<» 

(rear,  reversing,  of  the  Friek  traction  engine,  315-318 
Gooch's  link  motion,  sii-ss,  102 

points  of  compression  of  the  hanger  link 

in,  87 

Good,  W.  E  .  steam  reversing  gear  designed  by,  105-107 
Gordon  and  Maxwell  isochronal  pumping  engine,  347-349 
Governor  connection  of  the  Reynolds-Corliss  engine,  227 
the,  of  the  Armington-Sims  engine.  17>i 

Ball  automatic  cut-off  engine,  214,  215 
Buckeye  engine,  171-174 


354 


INDEX. 


Governor,  the,  of  the  Dexter  automatic  cut-off  engine,  220 
Ide  engine,  200 
straight-line  engine,  187-189 
Westingliouse  engine,  210 

Greene  automatic  cut-off  engine,  230,  231 

Griddle  valve,  example  of  a,  126 

Hanger  link,  effect  of  the  position  of  the,  on  the  port  open- 
ings, 96 

point  of  suspension  of  the,  in  Stephenson's  crossed 

rod  link  motion,  93 
Stephenson'e  open  rod 

link  motion,  70 

points  of  compression  of  the,  in  Gooch's  link  mo- 
tion, 87 
link  motions  with 

rock  shaft,  92 
Harris-Corliss  engine,  231 
Heater  of  Reynolds'  condenser,  255-259 
Hijfh  pressure  engine,  11 
Hoisting  engine,  gear  for  reversing  on  a,  103 

engines,  327-3-H 
Horizontal  engines,  11 

stationary  engine,  construction  of  a,  13,  14 

Ide  engine,  196-205 
Inclined  engines,  1 1 
Increase  of  lead,  93 
Indicator  diagrams  obtained  during  the  trial  of  the  engines 

of  the  S.  8.  Meteor,  303-308 
Ingersoll's  air  compressor,  338-342 

governing  mechanism  of  the,  340,  341 
side  elevation  and  plan  of,  339 
eclipse  rock  drill,  335,  338 
Injector  condenser,  Bulkley's.  245-248 

application  of  the,  247 

as  arranged  for  natural  water  supply, 

249 

independent,  254,  255 
Inverted  cylinder  engine,  1 3 
Isochronal  pumping  engine,  Gordon  and  Maxwell,  347-349 

James  and  Wardrope  engine,  211,  212 

Jet  condenser,  Knowles'  independent,  248-251 

application  of,  250 
with  safety  valve,  251 
condensers,  244 
Joy  valve  gear,  marine  engine  with  the,  282-285 

Kennedy,  A.  B.  W.,  research  committee  on  marine  engine 

trials  ;  report  upon  trials  of  the  S.  S.  Meteor,  296-309 
Knowles1  independent  jet  condenser,  248-251 

application  of.  250 
with  safety  valve,  251 
steam  pump,  342-344 

Lane  &  Hodley  Co. ,  design  of  an  adjustable  cut-off  engine 

by,  108-112 

Lap.  to  find  the  proportions  of,  33 
Lead  and  compression,  equalizing  of,  41 

cause  of  variation  of,  23,  24 


Lead,  equalizing  the,  in  Stephenson's  open  rod  link  motion, 

_ 79-82 

with  crossed  rods,  83,  84 
increase  of,  93 
of  a  valve,  17-19 

eccentric,  22 

to  find  the  proportions  of,  33 
variation  of,  in  crossed  rods,  83 

when  the  eccentric  is  shifted  across  the  shaft, 

140,  141 

with  the  Allen  valve,  increase  of,  85,  86 
Lidgerwood   Manufacturing  Co.,   hoisting  engines  by  the, 

328,  829 
semi-portable  engine  by  the, 

319 
Link  block,  effect  of  a  rocker  on  the  sliding  motion  of  the,  95 

to  minimize  the  sliding  motion  of  the,  94 
hanger,  points  of  suspension  of  the,  93-96 
motion,  finding  the  amount  of  variation  of  lead  caused  by 
shifting  the  link  from  full  gear  to  mid- 
gear  in  open  and  crossed  rods.  72 
position  of  the  link  in  full  gear,  68 

parts    for   full    gear    back- 
ward, 72,  73 
positions  of  the  parts  when  the  link  is  in 

mid-gear,  68,  69,  72,  73 
Gooch's,  86-88,  102 
in  full  gear  for  backward  motion,  65 

forward  motion,  65 
mid-gear,  66 

reversing  gears,  modified  forms  of,  102 
Stephenson's  open  rod,  64-82 
used  on  American  locomotives,  89 
with  crossed  rods,  8:2-84 
the  Allen  valve,  84-86 
motions  and  reversing  gears,  64-88 

valve  gears  of  triple  expansion  marine  engines, 

285-2S7 
with  rock  shaft,  89-107 

points  of  compression  of  the  hanger  link 

in,  92 
to  find  the  position  of  the,  corresponding  to  the  crank 

position,  92 

Lip  of  the  valve,  definition  of  the,  16 
Live  steam,  15 

edges,  15 
Locomotives,  American,  link  motion  used  on,  89 

direct  acting,  open  rod  link  motion  used  in,  64 

for  railways,  1 1 

steam  reversing  gear  for,  105-107 

Marine  engine,  275-311 

compound  condensing,  example  of  a,  276 

for    an-  ocean-going  steamship, 

279-281 

for  coasting  vessels,  279,  280 
small,  example  of  a,  276-279 
with  Douglass's  valve  gear.  285 

the  Joy  valve  gear.  282-285 
engines,  1 1 

triple  expansion,  valve  gears  and  link  motions  of, 
285-287 


Marine  engines,  varieties  of.  JT'i 

Mariposa.  engines  of  the  S.  S..  2*7.  Js>.  LM.III 

M.  ch:ini~in-  nr  vaKc  niotioiiji,  diagrams  for  designing,  33-63 

Meteor,  hollers  of  the.  '.".is 

engines  of  the.  293,  U'.'l.  2'.'/>.  i".ir,.  L".>S 

ob.MTvers  in  testing  the  engines  "!'  tlie.  308,  309 

report  upon  trials  of  the  S    S  .  ^.n1,-:;!!-.! 

test  of  the  engines.  of  the.  2'.n'i-:;o'.i 
Meyer's  eiit-otF.    los 
Mid-gear,  to  rind  the  position  of  the  parts  when  the  link  is  in, 

'.IL'.  n:;. 

Mills,  triple  expansion  engine  lor  driving,  266-270 
Mini,  engines  of  the.  ^7.  'J'.M.  L".H' 
Morton's  patent  valve  gear.  IN" 
Multi-cylinder  jenginc,  211,  212 

eiii-ines.   l.'i 

Mnltiported  valves.   I2d 
Mundy's  friction  drum.  :!27.  .'528 
hoisting  engine.  :;27.  :  ill-- 

New York  Safety  Steam  Power  CO.'B  engine,  214 


Offset  of  the  rocker  arm. 

to  find  the  am.  Hint  of,  S'.».  '.id 
Open  rod  link  motion.  Stephen»on's,  64-82 
(  (-.•iilatin.L'  engines.    1  1 
Over-travel,  eft'ert  of  giving,  to  the  valve,  97,  98 

Paris  Exhibition  of  1889,  triple  expansion  engine  at  the, 

286-270 
Philadelphia  and  Reading  Railroad  locomotives,  steam  re- 

versing L'ear  employed  on  the,  105-107 
Piston  and  crank,  relative  motions  of.  :'<\ 

valve,  action  of  the,  in  Ingei-soll's  rock  drill,  337,  338 
movement  of  the  straight-line  engine,  equaliza- 

tion of  the,  192-196 
effect  of  the  variation  between  the  position  of  the,  and 

that  of  the  crank  pin.  :io 
motion,  irregularity  of  the.  2O-24 

of  the  Porter-Allen  engine,  variation  of  the,  158-160 
of  the  straight-line  engine,  186 
position,  to  find  the,  for  a  given  eccentric  position,   141, 

143 
speed,  causes  of  the  variation  of,  20,  21 

nature  of  the  variation  of,  21,  22 
to  find  the  position  of  the.  34.  35 
Point  of  admission,  finding  the,  143 
cut-off,  15 

equalizing  the,  by  making  the  steam  ports  of 

different  widths,  98-101 
fixed,  evils  of  a,  144,  145   . 
to  find  the  amount  of  steam   port  opening  for 

each,  142,  143 
variation  of  the.  in  the  Ball  automatic  cut-off 

engine,  214 
varying  the,  by  shifting  the  eccentric  across  the 

crank  shaft,  138-143 
release,  means  of  prolonging  the,  25 
Points  of  cut-off,  equalizing  the,  39,  96-98 

in  the  Wheelock  automatic 
cut-off  engine,  236,  237 
to  equalize  the,  114-120 


Points  of  cut-off,  varying  the.  by  moving  the  cut  off  vahev 

120-134 

Portable  engine.  SI 8-327 
Porter- Allen  engine,  1 4."»- 1  di  i 

prominent  features  in  the  design  of  the,  145 
Port,  exhaust  edge  of  the,  15 

opening,  finding  the.  for  a  given  point  of  cut-off,  141,  142 
openings,  diagrams  of,  given  by  Btepheason'a  open  rod 

link  motion.  7t>,  77 
given  by  the  Allen  valve  with  link 

motion.  S4.  Sf>.  Sf. 
the,   for    the  longest  and    shortest 

points  of  cut  -i  iff.  13"),  l.'Ui 

effect  of  the  position  of  the  hanger  link  on  the,  96 
finding  the  amount  of,  fora  given  valve  motion,  60, 

61,  62.  r,:; 
in  the  Armington-Sinis  engine,  diagrams  of  the,  182, 

189 

Porter-Allen  engine,  diagram  of  the,  156,  157 
of  an  Allen  valve,  diagram  of  the,  31.  32 
a  valve  motion,  diagrams  of.  26.  -7 
cut-off  valves,    diagrams   of.    112.    114.   117,    118, 

119,  120.  121.  12"i.  126.  130.  131,  132,  133 
the  Buckeye  engine,  diagrams  of  the,  171 
steam  edge  of  the,  16 
Power,  measurement  of,  in  testing  the  engines  of  the  S.  8. 

Meteor,  300 
Pressure,  mean  barometric,  during  the  trial  of  the  engines 

of  the  S.  S.  Meteor,  301 
Pressures,  mean  effective,  during  the  trial  of  the  engines  of 

the  S.  S.  Meteor,  diagrams  of,  297,  300,  301 
Pump,  Knowles'  steam,  342-344 

of  the  Worthington  compound  condensing  engine,  263, 

264 

Worthington's  steam,  344-340 
Pumping  engine,  Maxwell  and  Gordon  isochronal,  347-349 

Quadruple  expansion  engine,  307,  308,  309-311 

Railways,  locomotives  for,  12 

Release,  proportioning  the  valve  for  a  predetermined  point 

of,  39 
Reversing  gear  of  Prick's  traction  engine,  315-318 

steam,  designed  by  W.  E.  Good,  105-107 
gears  and  link  motions,  64-88 
link  motion,  modified  forms  of.  102 
steam,  102-107 
Reynolds'  condenser,  255-259 

construction  of,  259 
sectional  view  of,  257 
top  view,  partly  in  section,  of,  258 
Reynolds-Corliss  engine,  221-229 
Riding  cut-off  valves,  108-137 
Robertson's  semi-rotary  engine,  329 
Rock  drill,  Ingersoll's  eclipse,  335-338 
drilling  engine,  or  rock  drill,  335-^338 
shaft,  influence  of  the,  upon  a  slide  valve,  23 
link  motions  with,  89-107 
of  the  straight  line  engine,  position  of  the,  192 
Rocker  and  frame  of  the  Buckeye  engine,   cross  section 

through  the,  168 
arm,  off-set  of  the,  89-96 


356 


IXDEX. 


Rocker  amis,  to  find  the  position  of  the,  91 

et-centric  and  valve  movements  of  the  straight  line  engine, 

191.  192 

Rolling  mill  engine,  reversible  gear  for  reversing  on  a,  103 
Rotary  engine.  329-334 

Rotary  engine,  advantages  and  disadvantages  of  the,  331 
engines,  13 

Saddle-pin,  shifting  the  position  of  the,  79 
Semi-rotary  engine,  difficulty  in  the.  329 

Robertson's.  329 
engines,  13 
Side  lever  engines,  1 1 
Silsby's  steam  fire  engine,  325-327 
Siphon  condenser,  244,  245 
Slide  valve  engine,  common,  11-32 

explanation  of  the  action  of  the,  14,  15 
influence  of  the  rock  shaft  upon  a,  23 
mechanism,  investigation  of  the  action  of  a,  33 
of  the  Ball  automatic  cut-off  engine,  216 
spindle,  14,  15 

variation  in  the  action  of  the,  14,  15 
with  rock  shaft,  23 
Sceed  attained  during  the  trial  of  the  engines  of  the  S.  S. 

Meteor,  304 

during  the  trial  of  the  engines  of  the  S.  S.  Meteor,  301 
regulation  and  the  use  of  the  auxiliary  springs  in  the 

Buckeye  engine,  diagram  of  the,  174 
Spindle,  slide  valve,  14,  15 
Stationary  engine,  horizontal,  construction  of  a,  13,  14 

triple  expansion,  with  cylinders  one  above  the 

other,  270-274 
engines,  1 1 

compound  condensing  and  triple  expansion.  260- 

274 

methods  of  compounding  in,  239-241 
triple  expansion,  266-274 
Steam  by  indicator  diagrams  during  the  trial  of  the  engines 

of  the  S.  S.  Meteor,  302-3»4 
cushioning  or  compression  of,  17 
distribution,  diagrams  of  the,  24-27,  114 
engine,  various  application  of  the,  312-349 
engines,  classification  of,  11-32 
expansjon,  27,  28 
expansively,  working  of,  15 
fire-engine,  325-327 
lap.  16,  17 

effect  of  the,  25 
live.  15 

object  of  using  the,  expansively,  27 
port  opening,  to  find  the  amount  of,  for  each  point  of 

cut-off,  142,  143 
ports,  14 

equalizing  the  point  of  cut-off,  by  making  the,  of 

different  widths,  98-101 
pump,  Knowles',  342-344 

Worthington's,  344-346 
reversing  gear  designed  by  W.  E.  Good,  105-107 

gears.  102-107 
rock  drill.  335-338 
.          wire-drawing  the,  13 
'    Steamship,  ocean-going,  marine  engine  for  a,  279-281 


Stephenson's  crossed  rod  link  motions,  point  of  suspension 

of  the  hanger  link  in,  93 
open  rod  link  motion,  64-82 

point  of  suspension  of  the  hanger  link 

in,  70 

Straight-line  engine,  185-196 
Sugar  mills,  Colwell's  engine  for,  321-323 
Surface  condensers,  244 

condenser.  Wheeler's  independent,  252-253 
Sweet.  Prof.  J.  E. ,  the  straight-line  engine  designed  by,  185- 
196 

Tandem  engines,  13 

Thompson,  J.  W. ,  form  of  diagram  employed  by,  38 

Throttling  engine,  13 

Throw  line,  definition  of  the,  17 

of  an  eccentric,  definition  of  the,  17 

the  main  eccentric,  to  find  the,  132 
Traction  engine.  ]  1,  312-321 
Travel  of  a  valve,  19,  20 

to  find  the  proportions  of.  33 

Triple  expansion  and  compound  condensing  stationary  en- 
gines, 260-274 
engine,  239 

engines,  examples  of,  285-309 
marine  engines,  valve  gears  and  link  motions  of, 

285-887 
stationary  engine,  diagrams  from  a,  273,  274 

with  cylinders  one  above  the  other, 

270-274 

engines,  266-274 
Twiss  engine,  237,  238 

Valve  action  of  Farcot's  compound  engine,  241-243 
admission,  of  the  Porter-Allen  engine,  149 

various  positions  of  the, 

149 
Allen's,  28-32 

construction  and  various  positions  of,  during  a  rev- 
olution, 28,  29 
increase  of  lead  with,  85,  86 
link  motion  with  the,  84-86 
and   cylinder  of  the   Armington-Sims  engine,    section 

through  the,  1 77 

straight-line  engine,  horizontal  sec- 
tion through  the,  185 
piston,  action  of  the,  in  Ingersoll's  rock  drill,  337, 

338 
movement  of  the  straight-line  engine,  equalization 

of  the,  192-196 
clearance  in  a,  19 

construction  of  a,  to  let  live  steam  follow  the  piston  dur- 
ing full  stroke,  15,  16 
the  Dexter  automatic  cut-off  engine,  219, 

220 

straight-line  engine,  189-191 
cut-off,  operating  on  a  fixed  seat,  1 34 
diagram,  Zeuner's.  42-63 

remedy  for  defects  of,  59 

eccentric  and  rooker  movements  of  the  straight-line  en- 
gine, 191.  192 
effect  of  giving  over-travel  to  the,  97,  98 


INDEX. 


Valve,  exhaust  edges  of  the,  15 

lap  of  a.  operation  of  the,   IS 

gear.  Douula.-s'.s.  marine  engine  with,  I's/i 

in  a  triple  expansion  stationary  engine.  -!'•'• .  274 

"Joy,    manne  engine  with  tin-.  2>2-2Vi 

Morton's  patent.  2*7 

of  tin-  Mr  engine,  construction  of  the,  2O2-204 
Keynolds  ( 'oi-liss  enirinc.  22.'! 
S.  S.   Mariposa.  2*7.  _'Jn 

mi  yacht  Mira.  construction  of  tln>,  2*7.  296 
Wheelock  automatic  cut  off  engine.  '_M  I    -••''< 
gears  and  link  motions  of  triple  expansion  marine  cnnine-. 

2*:.-2s7 

liavinir  over-travel,  diagram  from  a.  26 
in  the   1'orter-. \lleti  engine,  at    tin'  end  of  its  travel  for 

the  crank -eml  port.   \'i('< 
in  the  I'orter  Allen  engine,  at  the  end  of  its  travel  for 

the  head  end  port.   I  .V! 
lead,    IT-l'.i 

in  the  Ide  engine,  the  adjustment  for,  2(l4,  205 
lip  of  the.  16 

mechanism,  action  of.  of  the  1'orter-Allen  engine,  150-100 
in  which  the  valve  has  neither  lap  nor  lead,  30,  37 
motion,  diagrams  of  the  port  openings  of  a,  'Jii.  L'7 

findini:  the  amount  of  port  openings  for  a  given,  60, 

«],  82,  f,:{ 

of  the  1'orter-Allen  engine,  position  of  the   parts 

when  the  lead  is  set  for  the  head  end  port,  151 

the  1'orter-Allen  engine,   position  of  the.  at  the 

hcL'inning  of  the  stroke, 

ISO 

positions  when  the  head-end 
port  is  full  open.  1")2,  15I{ 
Westinghouse  engine.  L'os.  L'II'.I 

motions  or  mechanisms,  diagrams  for  designing,  33-63 
of  the  ArmingtOD-Sima  engine,  177 
jiositions  of  I  he  Straight-line  engine.  190 
proportioning  the,  for  a  predetermined  point  of,  39 


Valve,  proportion!  in  the  ArmingUm-Simi  engine,  181-183 

rod.  etl'eet  of  the  angularity  of  the-,  36 
to  draw  or  lay  out  a,  40—42 
travel.  Hi.  20 

definition  of,  14 

with  lap.  acti if  a,  15 

without  lap,  action  of  a,  15 
Valves.  Allen  and  common,  comparison  of  diagrams  from  the, 

30 
and  cylinder  of  the  Buckeye  engine,  cross-section  of,  166 

cylinders  of  the  I'orter  Allen  engine.   I4S-I50 
cut  off.  action  of,   1 10-1 1 ") 

setting.   I  IS 

to  find  the  amount  of  lap  for  the,  123 

varying  the  points  of  cut-off  by  moving  the,  120-134 
diagrams  showing  the  actual  working  of  the,  2t-L'7 
multiported.   iL'ii 
of  portable   engines,  319 

tlie  Buckeye  engine,  construction  of  the.  K>I-17I 

Iteynolds-Corlir-s  engine,  construction  of  the,  227-229 
to  investigate  the  action  of  the,  for  any  point  of  cut-off, 

127 
Vertical  compound  condensing  engine,  265,  266 

engines,  1 1 
Vessels,  coasting,  marine  engine  for,  279,  280 

Westinghouse  engine,  206--JI 1 

\V heeler's  independent  surface  condenser,  252-255 

Wheelock  automatic  cut-off  engine,  234-2:>7 

Wilson,  C.  J.,  analysis  of  Scotch  coal  by,  299 

Wire-drawing  the  steam,  13 

Worth,    Mackensie  &   Co.,   vertical  compound   condensing 

engine  constructed  by,  265.  266 
Worthington  compound  condensing  engine,  260-264 
Worthington's  steam  pump,  344-346 

Zeuner's  valve  diagram,  42-63 

remedy  of  defects  of,  59 


2  3  01  0  ft 


RETURN     CIRCULATION  DEPARTMENT 

TO—  ^      202  Main  Library 

LOAN  PERIOD  1 
HOME  USE 

2 

3 

4 

5 

6 

ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 

1  -month  loans  may  be  renewed  by  calling  642-3405 

6-month  loans  may  be  recharged  by  bringing  books  to  Circulation  Desk 

Renewals  and  recharges  may  be  made  4  days  prior  to  due  dote 

DUE  AS  STAMPED  BELOW 


JUL  3  0  1980 

Au>  $o  11*0 

<$&    3Q 

Q<~r  3.0 

P.ETD      JAN  2  9  198i 

crn  o  rf  1000 

rLts  ^7  Woo 

.<• 

AUTO  wstoffi  IMS 

UNIVERSITY  OF  CALIFORNIA,  BERKELEY 
FORM  NO.  DD6,  60m,  3/80          BERKELEY,  CA  94720 


U.C.  BERKELEY  LIBRARIES 


